there are 3 factors here...
1 - Have you done enough to obtain TM status?
2 - Are you able to prove bad faith?
3 - the actual doamin name itself
If you have been running a business and has been successful and active, you may be able to have a convincing arguement for common law TM. You will have to support the claim though. If it is only an affiliate site that has little hits and generates little money, it is less likely you will have protection. But if you have good traffic, have good revenue and you can show you are "well known" in a specific area, that will help you.
It seems obvious the other domain is being used in bad faith. Take screen shots and keep everything.
This is where we are on the other side of the fence and it isn't a fun position to be in.
