I disabled the "secure updates check"(enter about:config into the address bar, create a new boolean value, name it extensions.checkUpdateSecurity and set it to false)
I disabled version checking with the nightly tester tools.
FireGPG now runs smoothly in my Fx3b3 :-)

I really like Firefox 3. It would be great to make version for F3 available before the final release, so we could test it in the beta stage.
Main problem seems to be the secure update. Can't that be made available at tuxfamily? You'll need a new certificate though.

Cheers, Jan