Vista - DESPERATLY NEED HELP(windows connection issues)

well to start off at the begging I am a freelance graphic designer and make my living off my computer. normally my computer never lets me down but recently I've been having some internet connection issues and desperately need to get it resolved. i can browse the internet using moxillia firefox, but internet explorer will not connect. to make matters worst any program that need to make an incoming connections is also blocked. I can't even logg into yahoo mesenger as that is also blocked. it just all started getting blocked about a week ago. it looks like it might be security set to high but all secuirty is turned off and the firewall is turned off.

i desperatly need to get this fixed