Help! Ingame lag on single player.

Hey, after playing Stubbs at a friends house I was hooked right away. I finally decided to get the game for PC, but when I play it theres a weird lag problem I have ingame. If I hold down the forward key (W) for like 2 seconds, then Stubbs continues to walk forward for 2 more seconds. If I hold down the key for 10 seconds, he will walk forward and keep walking forwards for 10 seconds after I let up on the key. During this time I can't do anything else, like turn around, eat brains, etc. and it's making the gameplay nearly impossible. I tried turning down the settings but still no luck. I have a fairly fast computer and can run other games (such as Half-Life 2) just fine on high resolution, good quality, and everything. If anyone knows what my problem is or how to fix it then please let me know here or drop me an email at . Thanks a bunch for all of yall who help!