I don't know if it's my ISP or my router, but, whenever I query the Steam master servers for a new list of game servers, about 85% of the time I lose the ability to make new connections - I can't join any of the servers it returns. I exit out of the Source game and close Steam, but for a seemingly random duration of time, I can not access any websites through any browser, nor can I connect to any IM or IRC servers.

However, existing connections are okay - I'm able to continue to IM and chat over IRC if I had a connection to the server before I queried the Steam master servers.

I've got a new Linksys WRT54G router on the way, so I'm hoping that resolves the problem. It should be noted that this occurs whether I'm running my desktop off of its wired or wireless adapter. Switching to my Linux box yields the same problems (i.e., I look for new games on Steam on my Windows box and my Linux box is unable to make new connections).

This occurs both under XP (using PC-Cillin) and Vista (using Windows Firewall + avast! free a/v).

In the meantime, any ideas?

Weird. Is steam stealing your ports or something? Run netstat -b from command line to see what Steam is doing.

I'd suspect that Steam was somehow blocking the connections, but the denial of service continues even after Steam has been closed (and no longer appears in task manager).

Very strange indeed.

Sounds like your hardware firewall is the sucks and thinks you're getting a DoS attack.

Netgear

Yeah it's either a firewall going bonkers or it's overloading the router's ability to make connections, so it just stops making new ones.

Well, I just upgraded the firmware (it was blocking Guild Wars from connecting to the login servers), so, once I'm done downloading gigs of updates, I'll see if Steam behaves itself now.

This happens to me too if I query the main server browser in a steam game. It'll update the list, but I cannot get the info on a server for like 20-30 seconds as it just doesn't update it. If I leave Steam, my internet is blocked the same time as well (like you said)

I just get around it by either A) Waiting it out - not too long B) Usually on play on favorites anyways, and it doesn't do it then

I imagine it's my firewall as well (not the router)