Auto-alt Tab Occurs When There's A Network Connection?

I had this problem since I installed this game (GTA San Andreas). So, I found that it keep auto alt tab when I play GTA only. Not other game. When I restart, it is gone. and will occurs when I open GTA. So, i try to scan and delete the game and the problem fixed. Still, when I install FiFa 2011, it is also happening. So, I deleted the game but the problem didnt fixed. Well, I also download Sims 3. and when I play the game, I tried to remove my Tenda Wireless reader, then the auto alt tab is no more occurs. So, it seems like I have to play games without using internet. Which means I can't play online games. So, I am telling you guys that I am having problem with auto alt tab/ losing focus when playing game/using programs like google chrome. So, what should I do for know? I think it might cause of my Tenda Wireless Reader? I'll try to use wire into my wifi then.