Game keeps shutting down?

I have a serious issue with pso pc version 2. I have the game installed on my computer and i`m running Vista Home Premium. The problem is the game keeps shutting down and takes me back to the desktop. I get into the game just fine, but after about 5 to 10 of gameplay the game shuts down. Does anyone know why this happens and how i can fix it? I love this game and i just want to play. Any help would be appreciated.

Are you playing online or offline? Are you using full screen or window mode? It's important to note that if you play full screen, PSO cannot be interrupted. If your antivirus program, IM program, or anything else tries to open a window while PSO is running, the game will automatically exit. The screen dimming effects generated by the UAC on Vista/7 have the same effect. If you want to play the game full screen, you must close all such programs that might try to open windows before you start PSO. If you don't want to close your IM program and such, then you have to use window mode.

Thanks Aleron, playing in window mode solved the problem.