wireless network - specific web site access issues

[CelesteSF]

I'm about to tear my hair out on this one -

I have a powerbook G4 running 10.3.7 and recently acquired a Linksys 802.11g wireless router.

I have set up a network using basic factory settings. I can access the Web.

However, I cannot access many specific sites when I am using my wireless network. I cannot figure out the common denominator that is causing my issue - for example. I can BROWSE the iTunes store, but I cannot use its search functionality or buy music - it will just hang and not go there. I can access many regular sites, but not certain parts of sites. It just won't go there. (examples of sites that it won't access: www.salon.com, the support part of the Apple site...) Other sites, just fine.

To be clear, I can access these sites if I am directly linked to the DSL modem. It's just when I am using the wireless network that my ability to get to and use complex Web sites is impaired or non-existent.

My firewall is off. I have set no rules restricting access to certain domains or anything like that. I have set the router back to factory defaults. My signal strength is great, I just have this inexplicable inability to access things.

Any ideas???