Can't view certain sites, but can on another comp?

Hello,
Basically the situation is, on my computer (where there was no problem in my house, i'm using my parents internet at the moment ) I can't view certain sites but I can ping them. The sites include msn.com, hotmail. myspace, microsoft, and loads more and I can't use msn messenger. BUT I can access them using a web proxy site. There is no software on the router to filter sites, and definatly none on my computer. What makes this siutation stranger, on one of the other wired computers in the house, there is no problem, but on the wireless laptop in the house there is, and on the Mac in the house, there is but with differnt sites

Any ideas? I'm completely out of ideas

Matty
Thanks

MTU?

I did think that, not to sure how to change MTU size, because I looked in my registery where the file should be and it's not there :S

Google for 'DrTCP' it's a small program that will edit the MTU & RWIN settings (amongst others) for your NIC (although with Win-XP, RWIN is set automatically).

yeah I tried using that but there was no values in the box, and it didn't seem to make a differnece

Try reading this & then this first.

The default MTU setting is 1500 which is what happens when the MTU box in DrTCP is blank. If your MTU setting is the problem it will need to be set at a lower value; maybe as low as 1400.