I’ve tried the eval version and after going through the trouble to find out how it can be installed (see other posts in this forum) both the stand alone version and the IntelliJ interation have the problem of loosing the Mac OS X menu bar after a while. This is a shame since the IntelliJ guys just fixed that with 4.5 and now it comes back with the integration. The product looks quite ok and better than the competitors I’ve tried - sorry, if it stops working suddenly it is quite useless 
had the same problem on my OsX… after a few days inslaling and uninstalling I got a solution for this: erase the directory .vpworkspace in User/<your_user>.
Becouse the name starts with dot (.) is invisible for the finder, you have to erase it by shell:
- open a terminal
- swith directory to user (cd /Users/<your_user>)
- erase directory (rm -rf .vpworkspace)
- restart Vp_uml
