You don't give many details but I guess your problem is that you can't register the game because it is already registered with another key. You need to either register it on another computer so you can create the multiplayer account (you can then login with that on your normal computer), or delete the old registration file. The registration file can be found here:
C:\Documents and settings\your_username\TribalTrouble\registration
Mac OS X:
If this is not the problem, then please contact email@example.com
with more details, including your new registration keys.