Very wierd network problem

Hello,

I am having a very wierd network problem, and I hope that someone here could be of buttistance to me. Here's the dilemma:

1) I have a reselling web hosting account where I have a WHM control panel and I can signup clients, using the space and bandwidth that I am provided.

2) I was transferring files through FTP the other day to one of the sites that I host, when suddenly it stopped working, and the file transfer didn't complete

3) No other websites that I hosted would work, not through a browser, FTP, POP3 email through Outlook, or not even using the IP address that I can use to go into cPanel

4) First I buttumed it was the host, but I found out it wasn't them, and it worked on other ends

5) I figured out that if I use a free public proxy server, I can access my website and email through webmail

6) Next I buttumed that it is Comcast, so I give them a call. They have me hook my cable modem directly up into my computer (not through my router) and it worked fine, so they tell me to call Linksys (the manufacter of my router)

7) Let me explain my network configuration now. I have a wired router, which the cable modem is hooked up to. I then have a computer hooked directly into the router, a VOIP phone, a TiVo, and a switch. Connected to the switch (which goes upstairs) I have 3 other computers hooked up to. None of the 4 networked computer can access any of the sites without a proxy server

8) I call Linksys, and they have me change some settings in the router configuration page, and update some firmware, but still nothing. They aslo had me restarting the router, cable modem, and computer. Nothing worked.

Does anybody have any ideas? This is becoming very serious, and I need it fixed ASAP. Thanks.