I use Mozilla Firefox and when I try to download something, Firefox just freezes before I can see download windows, or download is complete and then it freezes.. I tryed to type link in Kget - it freezes too, Konqueror - same, Epiphany - same..
I can download with d4x or Opera but I can't with these browsers. What could it be? Maybe modem drivers?
Anyway, I have Intel536ep Winmodem on 2.6.8 kernel, and firstly I tryed with Firefox 1.0.4 and then I upgraded to 1.5.0.2 and it still doesn't work. Can you please help me to solve this problem?

Try opening a terminal window (xterm, konsole, gnome-terminal, eterm, et cetra) and typing The problem might be firefox or it might be something else.