Blank web browser with broadband

I have a strange problem with my broadband connection. It was fine until a few days back. But since then I can only seem to access a couple of sites (two academic UK web sites) - either using Safari, Internet Explorer and have tried 3 different computers (one at a time, all Macs, running OSX 10.3.9, Voyager 105 USB adsl). All the common sites such as google, bbc you name it just fail flash up the name in the URL box and then fail to load, and sit there with an empty browser screen. Weirdly, Mail (Eudora or OSX Mail) work fine as does an online game but not Apple's Software Update- it is as if some types of net traffic are restricted. The only site I seem to be able to access seems to be www.shef.ac.uk pages (I have used a vpn connection to it, but it is not active now). They load rapidly and I can go down many levels (so it isn't that they're just cached as clearing cache does not alter the rate of download). It is as if we've been limited to just a few specified webs sites. Resetting the browser, emptying cache and even reinstalling the Voyager 105 software does not help. The Voyager monitoring software and Apples Internet Connection software both tell me that the ADSL Voyager is working fine.

If I switch back to a dial-up using the same computers one at a time everything works fine.

Any ideas or am I just going mad???

Thanks for your help..

 

Cure for Blank web browser with broadband

Thanks for your suggestions. This turned out to be an ISP problem. They got around it by giving me a static IP address. Interesting that it worked fine for a few weeks, I guess they must have changed something at the ISP end.