Does anyone else have a problem where they can't add new materials to the library?  Once in ever 10 times I seem to get a plus icon, but most of the time I can't add anything.  The icon just isn't there.  I'm in the materials room and I've tried multiple runtimes. 

Poser 8, Windows 7 64 bit.  Any help would be very appreciated! 

I have Poser 8, Windows XP 64-bit.  I have to be in a specific folder in the Material room in order to add to the collection.  I don't know if this is peculiar to me but it's always been that way.

Which folder works?  One that came pre-installed or one you made?

 This has happened to me too.  If you restart poser it will work again.

"I have to be in a specific folder in the Material room in order to add to the collection."

I don't know whether it has to be a specific folder in the Materials Library (there are no folders in the Material Room, only materials), but you mean possibly the same, in my case the + icon is only visible when I'm in one of the subfolders in the Materials Library, which one doesn't seem to matter.

 You must be in the Material Room for the + sigh to appear. You can apply mats from everywhere but only add new ones from the Material Room itself.

So be sure you're in the Material Room tab :)

Quote - Which folder works?  One that came pre-installed or one you made?

It doesn't matter which subfolder.  I think I worded that incorrectly.  I make subfolders in the Material room for whatever I'm working on.  If I'm not in one of those folders I don't get the option to add a Material Collection.

 This happens to me from time to time when I try adding a new character to my library. I have to save the PZ3 and restart Poser. When I do the "+" re-appears.  The folder destination is correct- Poser just does not want to cooperate. 

Make sure you have got either the folder or an existing material positively selected (dark highlight). If nothing is 'selected' then the "+" isn't displayed