Password file somehow damaged - remove it
Is there a suspiciously long password in the password field (many "*" signs)? Then do the following stuff. You may also try the following steps if nothing else helped so far. Never try to open/edit "sys/usgn_pw.dat" to avoid such problems. Try the following to solve problems with damaged password files:
Quit CS2D
Go to the folder where you installed/extracted CS2D
Open the sub-folder "sys"
Delete the file "usgn_pw.dat" in that folder
Start CS2D
Enter your correct password again in the settings and see if it works!
Change your password at UnrealSoftware.de if the problem continues! (repeat above steps afterwards)

Open ur console
Put in:
usgn_user "name"
usgn_pw "password"
If you want to connect to another server you should do the same thing all over again.