Pinging game servers kills connection

When I use a game server browser such as Qtracker or Steam to scan for game servers my connection often goes wonky. My connections to IRC, Xfire and MSN all drop and even firefox becomes unable to connect to sites. The connection doesn't actually drop (that I can tell) as all lights are present and correct on my router.

In order to regain connectivity I have to login to my router and reconnect it, then it's fine. I've lived with the problem for a while now but it is getting very irritating and I'd like it to be fixed.

Do any of you know what might be causing it?

Router: Speedtouch 510 v4 via LAN
OS: Windows XP Pro SP2
ISP: Nildram BB2 1Mb

Why aren't you blaming the game server browsers?

Because I used to use game server browsers on 56Kb dial-up and never had any problems.