virtualbox.org

I didn't have any problems installing VB on the RC release, but installation on RTM fails (setupapi.dev.log):

>>> [Import Driver Package - C:\Program Files\Sun\xVM VirtualBox\drivers\USB\device\VBoxUSB.inf]
>>> Section start 2009/08/02 12:41:25.715
12:41:25.715 cmd: C:\Windows\system32\MsiExec.exe -Embedding E4F8BC0F12344F713D599CBA748A8781 M Global\MSI0000
!!! sto: 12:41:25.715 Using mismatched version 6.1.7600 drvstore.dll on version 6.0.6000 system. Error = 0x00000032
<<< Section end 2009/08/02 12:41:25.715
<<< [Exit status: FAILURE(0x00000032)]

No Google-hits on the "mismatched version drvstore.dll" string - is it just my installation that's botched?

Your assumption is possible. Another possibility is that Microsoft changed a few things on that level between the RC and RTM. Are you sure you have the RTM release? How did you get it? I can't imagine someone having the RTM already.

The RTM is out there, but as we have mentioned a zillion times already, MS changes things often until and including rtm versions, open a bugtracker ticket so the dev's can solve it.

Using mismatched version 6.1.7600 drvstore.dll on version 6.0.6000 system.

Looks to me like a mismatch of Microsoft versions. You did uninstall before you installed the RTM right?
If so then MS has some more work to do.

Perhaps this could also be caused by some pseudo-intelligent compatibility mechanisms.
VB 3.0.4 installed just fine here under Win 7 RTM x64 (6.1.7600.16385)