I haven't had time to experiment yet because I've been frantically backpedaling my group policy installation. Any time my users try to create a tab--by ctrl-T, or automatically opening a restored session, or opening bookmarks a tabs--they get the Firefox crash reporter.
When I get everyone back to Firefox 2.0.0.14 and my phone stops ringing, I can start experimenting.
I have been running Firefox 3 on my own machine with no trouble since the Mozilla release (and on and off before that, from beta 3), so I figured I was good to go. Also, I just discovered one of my users got the Frontmotion MSI for Firefox 3 with no tab trouble. I can't think of anything that's unique about him.
Ideas anyone?