unstopable Y- button insertion on Windows partition, while most mac-functions are out

Hi,
...in advance, sorry for bad english

Have only just started using Mac and have been very happy using it,
having had no bugs, flaws or errors whatsoever, up till now.
And to be quite frank , this one has me beaten ( not that that's too hard)

So, I was playing a game on the windows partition when I opened a text-screen to send a message. However it was rapidly getting filled with "Y"s
I'm not sure how and why ( pun intended) but at some point something happend (perhaps a lethal key-combination?) so that my computer kept typing "Y"s, I got the Y-button out of the keyboard and saw nothing wrong.
I put it back and started Mac, where I miracoulously didn't have any Y-problems, ( I then went back to Windows, where the Y-problem was still alive.)
Back on Mac, my Dock no longer enlarged when I scrolled over it, when I clicked menu-bars I have to move over the subdivision-options while keeping the mouse pressed, to go to them. Exposé only worked once in 100 mouse-swipes, etc.

Is there anyone who knows what's going on with my precious Mac?
what could have caused this... how to restore it ?
I'm at the end of my wits

Thanks,