Specific Web Pages Will Not Load

Facebook, Tumblr log in page, Pottermore and Apple pages will not load on any wed browser (Chrome, Firefox and IE) or any computer. All computers run windows 7 and one is very new. It seems to be getting worse as time moves on. The web browser will just keep spinning until it times out.
"Error 7 (net::ERR_TIMED_OUT): The operation timed out." (chrome)
I can access tumblr tags and blogs but not the log in page. My ipod will load both facebook and tumblr but only occsionly loads itunes store.
I have tried accessing the sites at through the library wifi and they work.
I think it is something to do with the modem/ router. But I do not know
The router is "Wireless G ADSL2+ Router
Would appreciate any help
Thanks

 

Managed to load facebook log in page but couldn't log in correctly as the graphics were all on top of each other. others still timed out. Also occasionally facebook loads but in basic version with no graphics etc.

 

Sorry but how do I do that. Does it matter if the local area connection is not working as the network cable id unplugged? Tried troubleshooting and it couldn't identify the problem.

 

Will try to connect to another network tomorrow.

 

I can access all sites on another network