internet explorer dns error

hey guys something crazy is going on. i used to be able to get to my favorite sites no problem. however now when i try to get to sites like wwe.com or magicthegathering.com i get an error, sometimes it is a cannot find server others it is a page cannot be displayed page. others (like with the-leaky-cauldron.org) only some of the graphics will come up then it stops loading the page.
what is going on?
any help you could give me would be appreciated!

 

well it has happened on all the house computers, and it only seems to happen with a few websites. all the computers have norton anti virus. i ran the anti-spyware stuff last night when the problem started.
i don't know much but i'll try to list what specs the computers have. my father's computer, a compaq presario with a 40 GB hard drive, a 256 MB RAM. my sisters is a balance with a 40GB hard drive, 512MB RAM. and mine which is a HP Pavillion with a 40GB hard drive, and 256MB.

i hope this helps

 

With so many computers, one would assume you are connecting them all to the internet thru a router. Have you tried simply shutting it (and your modem) off and back on, and see what happens?