I can confirm this (winVista FF 3.6.13)
The strange thing is that running his test userscript seems to mess up the new Goggle Groups interface history. This might make sense if nGG uses localStorage to maintain the history and calling localStorage.setItem, localStorage.getItem, or localStorage.length from within a userscript somehow TRASHES localStorage.
Note that the test script runs on
http://www.google.it/ and really shouldn't be able to affect
https://groups.google.com/(this 'trashing' may have also prevented my first attempt in nGG to reply to this from working).