My office has a simple Server 2003 set up, and at home I have a Tiscali broadband connection. We set up a VPN so that I can access my emails when out of the office, both on the home PC and also on a laptop - and this has performed reliably for over a year. More recently though, it has become very unreliable from the home PC. The VPN connects perfectly every time (ie. I can see the server in Explorer, and can list its contents, copy over DOCs, etc.), but when I click on the webmail service it often just says "Page not Found". After several reboots I sometimes eventually get through, but not always.
So I brought the laptop home and tested it. When connecting through its AOL dial up service, I could get emails from the office, but when connecting through the wireless link (which then uses the Tiscali broadband connection) it was back to being a problem. I then assumed it must be something up with Tiscali, but they deny making any changes, and implied that if I could connect to the server OK, then it wasn't them.