Overkill - Thanks for the warning. The name is not being changed. This game has been in development for a while, and we have a lot planned for the future. "Crossfire - the multiplayer RPG" both has a distinguishing subtitle from our games, and they don't appear to have copyrighted anything. They are also not listed as having paid for a registered trademark related to the title. Legally we are in the clear.
Just so that we're clear, this is not legally true. See http://www.uspto.gov/go/tac/doc/basic/register.htm
. You don't need to register a trademark to receive trademark protection, though it makes it much
easier to take action if your mark is violated. Legitimate use is enough, generally, to at least sue to prevent your use of the mark; damages are perhaps trickier to obtain without registration. Neither would a subtitle in their name be enough to protect you if it was decided that there was confusion between the products due to the names; for instance, any game that ends in "tris" is usually found to infringe upon the "Tetris" trademark, even if there are other things that distinguish the products.
Not saying that you should stress over this, but at least be aware that you're not automatically immune should they ever choose to start a fight, at least assuming they've been using the name for a while.