Help with windows98 & Microsoft

Hi, I'm new to the forum, but have a major problem, at least for me it is. I have not been able to log into MSN, but can log into AOL and Yahoo, but when I use browsers to search, many of the browsers will not open up for me, some will but most just time out or do nothing at all. I have installed AVG7 and do a daily test, but heres the funny part. I have connected three different computers to my one internet line, 2 of them with windows 98 and one with windows XP and all three computers are doing exactly the same thing. I think it has to do with the ISP or my modem, but my ISP provider when called said they think i have a virus of some kind in my computer, which sounds bogus since it is doing it on three computers. Also I have Lime wire and when I started having the problems with the web sites, all of a sudden I can't download anything from lime wire, says I have a firewall, never had one do that before, and haven't installed a firewall to my knowledge......Can you please help?, I am truely stumped on this one, and I am just an average computer person.confused

 

Thank you so much, I am headed to work but will give this a try and see what happens later tonight. I need all the help I can get...lol I'll let you know after words...Again Thanks so much!!