I've just tried to play Team Fortress 2 for the first time for quite a while, and I am afraid I am plagued with a very annoying issue.
When browsing for servers, I consistently see very good pings on the servers I previously used (~30ms). However, once I join an actual game I suddenly find myself with a ~800ms ping and everything becomes completely unplayable.
Searching the web, I suspected it might be the Multimedia Class Scheduler Service, so I turned it off. Sadly, that was no help at all, so I also tried this suggestion (to turn off TCP Auto-Tuning) to no avail.
I was once able to play TF2 just fine with my current network configuration, but with a different OS (I was on Windows XP, and recently installed Windows 7). My network card is a rather horrible Ralink Wireless card, which comes with its own configuration utility to set up network connections. Back when I was using XP, I would have similar issues unless I used the card's configuration utility instead of Windows XP's. While the configuration utility has a Windows 7 version, from reading some help files I tend to believe it hardly does anything other than provide an unnecessary coat of ugly paint over Windows 7's innate configuration.
If anyone has any suggestions, I would be grateful. In the event I break down and get another card (or punch holes in my walls for a wired connection), I'll be sure to update this with whatever effect such moves may have.