Add-ons: {972ce4c6-7e08-4474-a285-3208198ce6fd}:3.0.8
BuildID: 2009032608
CrashTime: 1239891698
Email:
InstallTime: 1239749186
Notes:
Obj-C Exception data:
NSInvalidArgumentException: *** -[NSCFString _getValue:forType:]:
unrecognized selector sent to instance 0x4128a0
ProductName: Firefox
StartupTime: 1239891694
Theme: classic/1.0
Vendor: Mozilla
Version: 3.0.8

This report also contains technical information about the state of the
application when it crashed.
--------------------
Could it have to do with these setting?

$ defaults read -g AppleSmoothAdvanceSizeThreshold && defaults read -g
AppleSmoothFixedFontsSizeThreshold && defaults read -g
AppleAntiAliasingThreshold
144
144
144