Strange keyboard behavior

Hello,
I have installed Vista and Windows 7 in dual boot. My keyboard is acting strange only in Windows 7. i tried usb and ps/2 keyboards and both are acting strange only in Windows 7.
While you type, there is some sort of lag, and if you type some word fast if lag happens, the word is typed in reverse order. for example if you type word "windows" it wlli type "swdoniw".
Also if you turn on "caps lock" it will type randomly lower letters.
for example: NNNNNNnNNnNnNNNNNNnNNnNnNNNNNNnNNnNn
caps lock is on, but it looks like it randomly type lower 'n'
Shift is not working every time, but again, sometimes looks like it is pressed all the time.
Once when some service reported stack overflow, my keyboard worked fine.
Please help.