wireless broken

hi, who can help me in this :

1- I have windows XPSP2,when I try to connect to wireless computer through
windows remote desktop , the log on success and ask me that the remote user
will log off ( yes or no ) , my answer is yes , then the connection broken
,what happened is that when I log off the wireless connection broken waiting
me to log on .

2- I configured the PC and join it to windows 2000 server domain , then I
try to log on with a domain user, but the log on failed and display this
message ( no domain available ) , but when I connect this PC to a wired
cable and disable wireless connection and enable wired connection , and log
on with a domain user , it works , after that I disable a wired connection
and enable a wireless connection , then I can log on with that domain user ,
it means that at the first time I must use a wired connection to log on.

Nasir sadi