If you still have problems after a re-install, check to see where the files are actually going and that they are valid.

There is a list of where they should be in the readme put out by the installer.

If you are using Windows Vista, there are some problems.  Sometimes it doesn't actually put the file there, but just a link to nothing.  I found the UAC in Vista to be too challenging and went back to XP.  Most of problems with Poser can be fixed if you re-install Poser itself outside of the default "Program Fileswhatever.." and use say "C:Poser7"