I had a similar problem after upgrading from stock 2.3.3 to rooted JVR 2.3.4. After the upgrade pretty much every app and background process constantly force closed - including launcherpro.
By pressing and holding the home button very quickly after I closed the FC messages I was eventually able to bring up the "recent apps" window, then select task manager, and from there I was able to uninstall LauncherPro.
However after a bit more mucking around I decided to do a factory reset, as pretty much every app on the phone was broken.
Before I did the upgrade I had backed up my call logs & sms messages, and used listables to generate a HTML file with all of my installed apps, and I used this list to install the apps I wanted to keep again.