FF3 RC1 Unable To Install Extensions

I've been using Portable FF3 since Beta4, all has been working fine. Today I updated to RC1 and lost the ability to install extensions and my existing extensions disappeared. So here's what I did.

1. Backed up my stuff.
2. Deleted all traces of FF from the USB drive and the system. Everything under Docs & Settings\App Data deleted. Everything in the FirefoxPortable folder deleted. All Mozilla related reg entries deleted.
3. Downloaded and installed Portable FF3 RC1 and installed to USB drive.

Ok. So clean install, starting over from scratch I try to install an extension via the extensions interface.
1. FF reports the extension is installed but I don't get the "Restart Firefox" button.
2. Installation button at the top is available but empty.
3. Manually restart FF3 RC1 Portable.

No extensions are listed. Extension I chose to install is listed as available to install again. (Doesn't matter what I install, I've tried several.)

Other bits of hopefully useful information to debug this.
(Mentioned in another thread) Two folders are created to the local HD and remain.
- C:\Documents and Settings\USERNAME\Application Data\Mozilla\Extensions\{ec8030f7-c20a-464f-9b0e-13a3a9e97384}
- C:\Documents and Settings\USERNAME\Application Data\Mozilla\Firefox\Crash Reports

On the USB drive, the only folder under \FirefoxPortable\Data\profile\extensions is staged-xpis. Which has subfolder, for what I assume, is the addon I tried to install.

This has, unfortunately, stopped me in my tracks and I'm hoping I can dig up a copy of Beta5 so at least I can get back to having a functional browser again.

Thanks,
--Chris