Computer problem

Ok i had this same problem before a while back and i cant remember how it got fixed. Problem:

I can connect to the internet and surf the web but i cant log onto ebay(ssl?) and cant do other secure logon things. I cant connect to anny instant messenger programs either. I dont remember changing any setting on my computer so i mind boggled. Anyone have an idea? I cant logon to my university email either.

thanks in advance =)