Ever since I upgraded to P8 I have run into a problem with materials.  Many times the "add to library" button is missing when I want to add a material to that part of the library.  Delete, new folder, apply, and fav are all there, but add is missing.  At first I thought it might be a Windows 7 beta problem.  But this is a clean install of the retail code, so I'm not sure that is to blame any more.  I do keep my runtimes on another drive (large data drive, my programs are installed on a fast but small SSD).  This is quite a problem, and despite lots of trial and error, I can't figure out why it pops up as a problem.  I think I've had the button show up before, but I'm not sure.  Anyone out there have any thoughts?  This is quite a problem for my work flow.

I'm running P8, Windows 7 64 bit.

 Click on any item already in the library and the button will appear.

Not for me.  I only get three or four buttons, add folder, remove, or fav.  This is just in materials.  In pose, figure, etc., I get all the relevant ones.  But in materials I never seem to get add to library.

 This is really odd. Clicking an existing item makes it appear fort me.

Opps. Poser Pro 2010 here. Sorry.

You are referring to materials.  You must click the material icon first in the upper part of the library to gain access to the add button.  Also you must select a folder or create one.

I realize people are trying to help, so hopefully this doesn't come off wrong, but I'm not new at this.  I have a library full of materials that I have added in the past.  I know how to add them, so I don't need to be told "click this then this."  Something has changed from P7 such that my install does not present the add button when all the other steps have been followed.

I have checked my own set up in P8, and every time I enter the material room, the Add button does appear.  However, currently I am running on XP.  Is your P8 installed into Windows 7 Program Files folder or is it in it's own folder on the core drive?  If it is in Program Files, do you have all security authorizations in place?  And have you installed all the Service Releases? 
This is information you didn't provide in your OP, and it could conceivably be something blocking access or perhaps an upgraded not yet installed.

I had the same issue a couple days ago, I couldn't get the add button to appear in the material room. If I changed rooms it was there for other library options, just not material room. Restarting poser did fix it.

Have had the same problems when trying to save each of the types of props, characters etc to their respective places. I can usually get round it by saving the pz3 file, quitting Poser then reopening it. Most of the time this works and the buttons will appear. Athough I find it much easier finding stuff in the new library panel it does seem to be a memory hungry feature. It can be like a web page that needs to be reloaded because some of the stuff doesn't load properly the first time. Then again my computer is about 7 years old!

hborre, it is installed in Program Files.  I don't think the permissions thing was the problem (read below for my fix) because I had problems with Sketchup trying to write to the program files folder and the files ending up in a protected folder, part of UAC I think.  Anyway, I have all the software that might do that authorized to write there. 

Anyway, I think I have found a fix that people might want to try.  I knew that the library was displayed using flash, so one of the first things I tried was updating to the latest version of Flash in my default browser (firefox).  But that didn't fix it.  For some reason I tried the same thing in IE instead.  That seems to have fixed it for me.  I'm not sure why, but it worked last night and was still working when I loaded Poser just now to double check.  So I'd be very curios if that helps the other posters who have a similar problem.  Give it a try and post back if it corrects it for you guys as well.