Are you trying the option "Save as: Ask when creating pdf"?
I used primopdf for years - then, just stopped working, tried reinstalling but nothing. I always used the option "Ask when creating pdf".
So I tried the option "Specific folder", it asked me for a folder, and saved my pdf there. NOW I can select the "Ask when creating pdf" option and it will present the folder I identified when I tried the "Specific folder" option, but I can select what I want and it now works again.
Hope this helps! It was a very random thing to just stop working after years of trouble free use, it must have lost some config info.