I am having problem with the DNS resolver on my debian box. The problem arises when I use wireless network and use UDP for DNS request.

The problem is that the resolver always fails with a timeout in connection. It happens only when I am using my wireless card with some wireles access points/network. I have tried troubleshooting with dig. dig complains that it cannot connect to the name server after some timeout, although a tcpdump shows that the packages are actually transmitted and some response message is also received. However, if I use +tcp option to force dig to use DNS over TCP rather than UDP, there is no problem. It is not the problem of the name server coz other users, and even the same machine when wired network is used instead, can use the name server flawlessly. Anybody has similar experience or any suggestions? I have been searching google for a way to force resolver to use TCP but got no luck. Any suggestion will be highly appreciated.

AFAIK there isn't a way to force the default name resolution to use TCP over UDP. My advice is that if you have pinned it down to only wireless on one system that appears to not be able to handle UDP transmissions, it's probably bad hardware/driver ie bad NIC and should be replaced. I've never seen wireless that could hold a TCP connection but not a UDP one, so my guess is there is some layer 2 thing it's not doing right.