LOTRO Locking up and crashing

Hello,
My girlfriend and I are both playing LOTRO trial accounts. We are both using MACs and playing via crossover. The game works fine when only one of us is playing, but when the second logs in, the game locks up on one of the computers then the other within 10 min.

Our connections are through a wireless router. I tried connecting one computer to the LAN line, but this did not help.

Do you have to do anything special to play two accounts over the same DSL modem with a wireless router?

Any help/advice would be greatly appreciated.

Thanks