Iceweasel weird behavior

["Alex S." <bytheclouds@ukrpost.net>]

Hello all,

Few days ago, I started having weird problems with my browser
(freezing on pages, freezing on downloads, freezing on opening
preferences even). After some tinkering that I did, I now have one main
question.

What is the difference between me manually typing 'iceweasel' to
terminal and me starting Iceweasel through panel/shortcut/system menu
(and with "run in terminal" flagged, it doesn't make any
difference). Because in the first case, the problems are non-existent.
In the second, they are there.

I suspected, at least, that the freezing when I try to download a rar
archive is due to some misconfiguration in Iceweasel's default
applications for the given content type, but after changing some
defaults in Iceweasel (started from terminal), the Iceweasel (started
from menu) now freezes on clicking "Preferences" >(

I'd be grateful for any ideas.
-- 
Time is an illusion. Lunchtime doubly so.

Best wishes,
Alex S.