IE 6, Help needed.

I have 3 computers, A Laptop (P4 2.8Ghz, 512mb Ram, 60gig HD), 2 desktops, PC "A" (AMD Athlon XP 2200+, 512mb Ram, 225gig HD), PC "B" (AMD Athlon XP 2000+, 512mb Ram, 80gig HD). All are completely up to date with upgrades for XP Home.
I have a 3Com cable modem connected to a D-Link 2.4Ghz Wireless Broadband Router connected to PC "A" 10/100 NIC via CAT5 wire, PC "B" 10/100 NIC via CAT5 wire, Laptop via D-Link wireless NIC.

bandwidthplace.com reports the following for all 3:
Communications: 1.9 megabits per second
Storage: 235.5 kilobytes per second
1MB file download: 4.3 seconds

The problem is:
PC "A "'s internet performance on some sites. Some sites load normal such as Yahoo, Google, MSN, Disney... as do searches on Google and Yahoo but some do not such as Windows Update, eBay, this site (windowsbbs)... which take minutes to load instead of seconds.

The Laptop and PC "B: work fine and all sites and load instantly.

Things that I have tried:
Reload NIC drivers
Change CAT5 Wire
Change ports on the Router
Reset Cable modem
Connect direct to cable modem
Reset Router

 

Try emptying the cache (IE>Tools>Internet Options>Delete Files button). One dodgy file in the cache can create the problem you're having.