Maybe everyone has discovered MOHAA Spearhead??
Seriously, maybe its just no-ones joined it! I've set up games (Spearhead) before - nothing wrong with my set up and no-one comes in.
Whats your Ping like? If high, people will avoid.
Sorry i can't help with the specifics of the game (don't have it) but if you are running a slow connection then it puts people off.