My UT99 and UT2004 servers suddenly stopped working with Gametracker. Both server info pages say the servers are 'Dead', and when I click 'Dead' and then 'Update scanning parameters', I get 'Could not scan server'. Both had been working fine for several weeks.

Both servers appear in their respective game client Internet server lists, as well as on other server trackers like Qtracker. I'm able to join both servers.

Nothing changed on this end, although there was a brief Internet outage just before the problems started. Both servers have passwords, which I suppose might be a factor. The UT2004 server is using non-standard ports, but like I said, it was working fine before.

Neither of your servers is showing (scanning) up in HLSW.

I suggest you check each of these links;
General connection issues;
http://www.gametracker.com/forums/forum.php?site=1&thread=108248

Gametracker IP addresses for white listing
http://www.gametracker.com/forums/forum.php?site=1&thread=108247

It turns out my WAN IP changed last night. Not sure why three of the five servers on GT adjusted automatically, while the UT99 and UT2K4 servers did not. Guess I'll have to reclaim them.

You may want to consider the dns option explained here;
http://www.gametracker.com/forums/forum.php?site=1&thread=108256

Just be aware that if you use dns instead of a hard set IP address on Gametracker that changes of IP are not picked up instantly.

When I first claimed those two servers, I used the WAN IP address, rather than the domain name common to all my servers, that I used for the other three. When I reclaimed the two servers, I used the domain name. So hopefully that won't happen again.