Can anyone give me a hint what I might need to do to get rid of the following problem?  I'm trying to make a render with the Rozhair and I've checked and double checked and triple checked and all the materials have all the same nodes except for transparency value but I can't for the life of me figure out how to get rid of these black stripes running through the hair when it renders. You can see in the attached image what I mean.  I'm pulling my hair out on this one, the black stripes even show up in the material preview but I can't figure out why.  If I remove transparency from the primary "hair" material the black areas disappear from the preview but still show up in the final render.  In fact any material I up the transparency value on becomes black in the render. Can anyone suggest something to try please?  I thought maybe the background colour was the problem but changing it to whatever has no effect, tried the scene background colour and also the transparency background in each of the material nodes, most importantly the trans map one, all to no avail. This is driving me insane, I can't figure out why upping a material's transparency would consistently turn it black.

Well, it's 1940's movie star hair, so naturally it has a roll of movie
film tangled up in it. 

More seriously, could a transmap node be accidentally connected to
a diffuse color input?

I'm also not seeing any shadows.  bad AO/bad shadow settings? normals forward?
where does one download or purchase said hair?

Nope, no nodes connected to something they shouldn't be.  Sorry, you'll have to elaborate, not sure what AO is, as for "normals forward", that sounds like a modelling problem, I hope that's not it, I don't know anything about modelling.
For all materials the transmap is connected to trans and trans edge, diffuse and specular colours are both connected to a node with the tex map.
The hair came from here actually, http://www.renderosity.com/mod/bcs/index.php?ViewProduct=17983 .  It's an oldie but a goodie, just hadn't had the notion to use it much until now.

Normals forward is a box you can check on the main part of the hair material.
It's near the bottom of the main 'Poser surface' node.   Often when you see
black facets, it's because the facet is pointing backwards, and checking
'normals forward' commands Poser to turn the facets forward.

Click to enlarge:

Normals forward is shown in this diagram. Try clicking on all the hair parts and checking Normal's forward.

Something weird is definitely going on.  The main material is apparently the cuplrit and I agree it does LOOK like the trans map is being applied as a texture, but there's no such connection evident anywhere I can find in the GUI.  To further confuse me if I nuke the main material's transparency node the material preview is super dark for that material, but not any of the others.  Even though they all have the same main mat'l settings and all have their Diffuse and Specular colours connected to simple image nodes with all the same text map and the base diffuse and specular colours are all white.

Hm.. maybe I'm behind the times.  I'm using P5, so there's no "normal forward", no advanced tab at all for that matter.

Turns out I already had this hair, but had forgotten about it.  When I went to buy it just now, because I liked the looks of it in your picture, the marketplace told me I'd already bought it... so I re-downloaded and re-installed.

And here's what it looks like on Eternal Judy, with the "Ginger blonde" matpose.

Exactly the same problem you're seeing!

The brown color doesn't have this problem.

Normals forward doesn't solve it.

Well poop...  at least I know now I'm not the only one with the problem though I think it's there with the brown mat too, just not as obvious.

I appreciate everyone's efforts to help, maybe in the light of day tomorrow some potential solution will become apparent, as it is I gotta knock off now to avoid being completely zonked at work tomorrow.

Agree that it's also there in the brown but not as obvious.

My best guess is there's a problem in the transmap itself.  Those "film" areas are
pretty clearly visible on the transmap, and they don't seem to agree with the
color map somehow.

try plugging the difuse node into the alternate diffuse . There was another hair that had similar rolls or curls and that seemed to fix it . (or maybe it was the other alternate channel)

Good suggestion, but didn't help. 

I have the feeling this one curl is outside the UV map, or maybe
the transmap doesn't agree with the UVmap for this one curl.

There's a blank line in the OBJ file that looks like a usemtl line
was removed ... maybe this one curl goes with those facets,
and it was meant to be a separate material zone. 

Try to contact the creator of this hair, as for me it seems to be an issue that normally shouldn't be there for a paid hair object.

I did notice on the two images of the transparency_edge - 1 is set to zero( "Ginger blonde") and the other is set at 1 (I think that is the default mat). Try changing the transparency_edge on the "Ginger blonde" to 1. I also own this hair but not at my Poser system right now so I cannot see if that makes a difference.

Good catch, but also didn't help.

Well it is was worth a shot.

Fixed. 

The first guess turns out to have been right.... it was reversed normals,
but for some reason the Normals Forward calculation wasn't able to find
and fix them.   I took the OBJ file into Amapi and flipped the normals manually
on the offending curl.

Since I won't be able to distribute this, maybe I should check with Rwaller and
see if he wants to have the revised OBJ for distribution.

Cool.  In the meantime I'll see if I can figure out how to do the same to my local copy, maybe I'll learn something in the process :)

I've PM'ed Rwaller, telling him of the solution.   If he permits, I could send
you the RTE difference file.

Edit: If you have Hexagon, you should be able to flip the normals. 
I don't know if Wings3D has that ability.

Doesn't look like Wings3D will do it, but I think I figured out how to do it with Anim8or.
{edit} my mistake, I could do it with anim8or if only there was some way to select facets without also selecting all facets behind as well, and if only the point select tool worked.  As it is there's no way in anim8or to select only the facets that need to be flipped, but the flip command is there, mocking me.

It's official, I'm going insane.  I flipped the normals with Anim8or and saved, but now everything renders only to the preview material.  Arg!

All you have to do is just disconnect the bump map from the gradient bump and rehook it up to "bump" and set it to a low value. I chose .01

Here is a picture.

Here is the result

Quote - Hm.. maybe I'm behind the times.  I'm using P5, so there's no "normal forward", no advanced tab at all for that matter.

Unfortunately with Poser 5 you have to do normals forward manually, here are instructions courtesy of randym77 who posted these instructions to me a couple of years ago.

Quote - To reverse the normals, use the grouping tool. You will have to do it for each existing group. Select a group, click "reverse normals," then select the next group and repeat until you've done all the groups. Test it by rendering; you'll probably see if you've missed any groups. Save the wings to your library, and you'll never have to do it again. They'll take the same textures and poses as the original wings.

Quote -

Here's the grouping tool in P5 (it's similar in P6). It's that button with the dotted box. The group you select will turn red, the rest will be dark.

Funky, things I never knew I could do with P5.  I'll take a stab at it.  Thanks.

if not mentioned above, vendor of said hair has promo render of blonde tex
without black bands, indicating vendor may know how to fix this.

I assume that importing hair obj geom with "normals consistent" checked, then
exporting (with all boxes unchecked) would not suffice to correct the bad normals.

Excellent, I was able to deal with it with the grouping tool.  Thanks for all the help everyone!