What Operating System are you using? ( I'm not familiar with Vista, 7, 8 )
What version of BF2 are you using? (DVD Edition, Deluxe Edition, Steam Version)
Can you start Battlefield 2 and join a game without problems?
Did you update BF2 to Version 1.51?
Did you download and install both parts of Forgotten Hope 2? (1 of 2) (2 of 2)
Actually I admit that I got no clue and never had the problem. But the answers to those questions might help others sorting the problem.