Newbie Question - Linksys WRT54G - Can't connect to Hotmail or AOL Mail

I have a desktop running Windows XP Pro connected by cable to my
Linksys WRT54G router.

I have another desktop running Windows 98SE connected wireless via a
Linksys WUSB54G adapter.

After many false starts I finally got both to work.

I can connect to almost all web sites that I use but I can't connect
to Hotmail, or AOL Mail, or Wikipedia, or Hartford Courant news.

If I bypass the rtouter and connect directly to the DSL modem, I can
connect to all of them.

Has anybody ever seen this problem?

I'm running Symantec Internet Security on both desktops.
I've turned off the Windows firewall.

I have the linksys firewall enabled.

I'm baffled, which is not new because I was baffled for two days until
I got the router and adapter to cooperate.

Shelly