Meanwhile my environment:
OS: XP SP3 (the same on Vista Ult. x86 + Win7 Ult x64)
FF: 3.6.12
Google Toolbar: 7.1.20101113Wb1
NoScript: 2.0.7
Still deactivtion of NoScript is solving the issue - but this is no option at all. Also to give permission for all sites and restarting firefox.
Today I've tried the suggestion made by Alan in the old thread:
- I've creatied a new windows user with admin rights
- active extensions are only NoScript and Google Toolbar; all plug-ins like Flash Player deactivated
- all google cookies deleted twice
but no success at all

Please provide me any questions or hints, I'm going to try everything to get this issue solved finally.
(P.S. I've tried it with Firefox 4 Beta 7 - same behaviour)