Steam won't open tf2 help please!!

i've had tf2 for a long time and played it with no problems but for some reason now every time i try to open it shortly after a error messager appears saying

"the instruction at 0x380dc0d0 refrenced memory at 0x00000010 could not be red click ok to terminate program

SOMEONE PLEASE HELP

right click TF2> properties>local files>view integrity of in-game cache

see if that helps