in the left frame of firefox, very often no content shows and the area is empty after the updatescanner icon in statusbar is clicked. but the content will appear when you click the icon many time. I dont know the reason,maybe updatescanner confilicts with some other plugin, tmp? ietab?
firefox 3.0beta5 updatescanner 2.109version no contents display
It would be very useful if you could try disabling your other extensions, to see whether one of them is conflicting.