Well, we can rule out ISP problems I think for now.
Have you tried cleaning the cache/temp internet sites ? Sounds to simple to try, but has worked before to solve these kind of problems.
Also, a bit related, if you go to start -> run and type CMD you get a nice console window.
Make sure you're in the root (C:\) and type
del /s *.tmp
This will delete all files in all directories ending with tmp that aren't in use (quit as many programs as possible when doing this). (Use at your own risk, some file sharing programs and programs like DAP use .tmp files as well)
If the above doesn't work type the following in the same console box;
ping
www.amigaworld.netYou should get a reply from 69.64.33.58.
Let us know what happens.