cant access many web pages

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i am with tiscali in england

first, about two months ago, i could no longer access my hotmail account
then a few weeks later, myspace.
then i couldn't watch videos on youtube
access facebook
bid on ebay
the latest casualty is itunes, which loads up, i can search for stuff, even preview, but cant buy!

usually the error message is
your connection has timed out
because it tries and tries to get the pages.

i am having a series of infuriating mails with tiscali, who say their servers are fine.

i'm using a macbook with os x 10.4.11
i have an ewire wireless router and airport express connected to that.

it's bizarre because i can access any other sites and even watch videos that arent on youtube, for example at the guardian's site.
also, i can access all the sites at ANY OTHER WIRELESS NETOWRK!
i am so tired and just want this to unravel
any clues?

i have deleted cookies.