Tab image changes when hovering over tab

Hi,
since one of the older nightly builds I get wrong behavior of the tab images 
- when I hover over the tab, the tab image changes to a "default" image (the 
one you get for empty tab). After moving mouse off the tab, the original 
correct tab image appears again.

Expected behavior: tab image should not change

My settings are:
Show load indicators on tabs: NO
Favicon on tab: YES
Siteicon on tab: YES
Close X icon on tab: NO


-- 
	Bye, Evzen