Mouse Lag maybe?
I have a new box running 3570k/asrockx4/xfx7870 and I just finished with the boat load of updates for win7. After fixing acouple java mess ups and reinstalling the os acouple times it's finally running like it should. Kinda. I splurged on the cpu/gpu/mobo and didn't get a monitor I figured the super sweet 46in samsung7k series(240hz 3d 1080p-yeah 3d was a bad idea but it looked good) I have would work until black friday rolls around and I can get a bargain on an ips monitor. I'm using an HDMI from the computer to the TV. I'm using a microsoft wireless comfort 5000 keyboard/mouse and experiencing mouse lag just piddling around the internet. While it's not a deal breaker it's annoying enough that I don't want to try to play a FPS because of it. I thought it was the cheap mouse but it works fine on my old laptop. Could it be a device/driver/hdmi cable or is my TV just so awesome that I need an actual monitor to get the most out of my new computer?
I have a Microsoft wireless mouse as well, and when you plug it in for the first time it wants to run a program called Microsoft intelli mouse or something similar. If you don't allow it to run at all, the mouse experiences weird lag and strange behavior as you are experiencing.
Try running Microsoft update with the mouse plugged in and go to the custom selection, and look in the hardware section to see if there are any mouse related updates.
The other idea is to look on the MS site for actual drivers.