First, an outline of my network: One site has an ADSL router connected to a switch connected to our main exchange/file server (Windows SBS) and a bunch of computers and a wireless antenna.
That wireless antenna goes to another wireless antenna at our other site which is connected to a switch along with a bunch of computers and a file server (Windows 2003 Server).
The problem we're having is some computers (they change) have extremely slow internet, usually to the point that the page times out. The computers are still able to ping the site hostnames though (with normal ping times) so it's not a connectivity or DNS problem.
We've tried replacing the router, and have had our ISP in doing some tests so know it's not their fault.
Any help greatly appreciated, as we've been tearing our hair out over this!