In my earlier Manually Updating Add-ons to Work post I had added the warning: Forcing an add-on to work can cause unwanted behaviours including browser crash upon start-up. Familiarize yourself on how to use Firefox Safe-Mode. In the course of forcing an install of GreaseMonkey into Firefox 3.7a6pre (Minefield), this caused a major unwanted behaviour thus the reason for that warning.
I had already forced several add-ons to work with Minefield. I restarted Minefield to complete the add-ons installation. Everything was going fine at first then suddenly I noticed Minefield kept opening the Greasespot (the official blog of GreaseMonkey) site in a new tab. Normally this should only happen once and on the first startup after install. In this case it just kept opening in a new tab. I tired to go into the add-ons manager to disable/remove the add-on with Firefox 3.7 the add-ons manager now loads in a tab instead of a separate window. I had no choice to close Minefield (after changing the preferences to NOT save my current open tabs). Restart Minefield in Safe Mode, went in and uninstalled GreaseMonkey. Upon restarting Minefield it appears to be behaving normally (well as normal as an nightly build would behave) now.