I think there's a shortcut combo of keys in Vista that I'm probably hitting during gameplay. Dunno why it starts lagging once I change the language settings though.
Pressing shift and alt switches between an English and US keyboard. It might be a similar combination you're pressing. Have you tried Googling the issue?
Don't eat peyote while playing TF2. Last time I did that the pyros flames came out the monitor and lit my keyboard on fire and it got on my hand and traveled up my arms then I was engulfed in blue flames the fonts turned to mayan symbols then I was suddenly an eagle over the amazon rain forest soaring in the air my vision was so acute I spotted a mouse on the jungle floor about a mile away I dived straight down and grasped the mouse with my talons and began to eat the animal alive tearing it apart with my beak. I remember thinking to myself "I usually don't eat like this"
The next morning when I woke up I was naked in the backyard and when I went back in the house I was kicked for being away from console on the TF2 server.
Yeah, just disabled the language input shortcut in the control panel. Worked like a charm. I have no idea why I start lagging when the input mode is in Chinese, though.