I found a workaround: in KDE control panel, appareance, GTK styles and fonts, if I set "GTK styles" to "Raleigh", Iceweasel works flawlessly.
So maybe it's theme-related... Again, more info can be provided if needed. Thanks Nicolas -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org