More Computer Whoes

ARGH!
For some unexplained reason, my laptop sometime around the end of July, gives me error messages for Mizilla Firefox and Internet Explorer. I can log into AOL, and read and send email but the welcome page also shows an error. With Internet Explorer I can get google.com to show up, and the first page of yahoo.com but I can't sign in to my.yahoo or most other pages. I can't even open most pages I think those two (my.yahoo mainpage and google main page) are the only ones I can get to on Internet Explorer, I can't get nothing with Firefox. I tried reloading the silly network thing for AOL, which just makes the computer think you are brand new to AOL ugh, at least you don't have to start a new account. I can't for the life of me figure out what went wrong. BTW I have to use other computers to access all my stuff that isn't email. It is a royal pain. My spyware and virus detector programs come up with nothing. To make matters worse my laptop for the last few months likes to overheat and shutdown sometimes, so it looks like I will need to get it fixed or get a new one but I can't afford to do either at this juncture in time.