I have same problem. My system is ubuntu 9.10 (i386).
firefox:3.5.4+nobinonly-0ubuntu0.9.10.1 ubufox:0.8-0ubuntu1
Extensions: Adblock Plus Adblock Plus: Element Hiding Helper Chatzilla DownloadHelper DownThemAll fireftp Flagfox Flashblock Java Console QuickProxy Russian spellchecking dictionary Tab Mix Plus Ubuntu Firefox Modifications
Disabling Tab Mix Plus and/or Ubuntu Firefox Modifications solves the problem
I have same problem. My system is ubuntu 9.10 (i386).
firefox: 3.5.4+nobinonly -0ubuntu0. 9.10.1
ubufox:0.8-0ubuntu1
Extensions:
Adblock Plus
Adblock Plus: Element Hiding Helper
Chatzilla
DownloadHelper
DownThemAll
fireftp
Flagfox
Flashblock
Java Console
QuickProxy
Russian spellchecking dictionary
Tab Mix Plus
Ubuntu Firefox Modifications
Disabling Tab Mix Plus and/or Ubuntu Firefox Modifications solves the problem