Control key intermintenttly locks down

A very vexing problem, that sets my hair crawling in frustration for about one hour cumulatively, every month, wasted on dealing with it.

I have a Samsung series 9 ultrabook, i5, 4GB RAM with windows 7 home premium, all updates installed. About 6 months ago I noticed this problem- every few days, out of the blue, the keyboard starts acting up:

basically it seems like the control key is pressed down even though its not; a reboot always fixes it, but its highly annoying to have to reboot when in the middle of work with 20 open tabs in firefox and tons of unsaved documents.

How do I know that its the control key? I am only guessing, but what happens is that some keys (only some) act as if control is pressed, e.g. in notepad I try to type H and get the "replace" window.
Most keys still work fine; so its not purely a "control held down" problem. its only some keys that behave as if control is pressed, I think it is C, V and G. The other keys work. I know its not a hardware problem because:

1) A reboot fixes it instantly- until the next time
2) This problem happens whether on the built in keyboard or an external USB keyboard
3) this problem sometimes only happens in firefox/chrome's URL address bar; and in the windows START "search programs and files" bar; but sometimes it happens globally in windows.

I tried:
looking for apps responsible (and shutting them all down - doesn't work - its a WINDOWS problem, not an app problem)

* Turning off all "accessibility" features- used to solve the problem a few times, now doesn't have any effect
* Updating bios, windows etc; running ccleaner, other system cleaners, virus / malware scanners and optimizers, etc.
* removing keyboard drivers from device manager, rebooting and reinstalling them
* Shaking the ultrabook senseless (luckily its SSD so it can take it)
* trying an external keyboard - the problem is duplicated there also (when it happens).

I thought of a system restore but for some mysterious reason, I have no restores left (I used to have it running all the time but now it says it can only go back a few days at a time, which always fails when I try it - says "restore failed". Is it all a virus that is set to annoy me and blocks the system restore?)

The only thing that sometimes fixes it without rebooting is rapidly pressing all shift, alt control and windows keys madly for a few minutes. Sometimes performing this tribal ritual takes 10-15 minutes to get rid of the problem, because I refuse to reboot! I have too many things open and in progress, and I won't remember where I was in half of them if I reboot. (Hibernate resume doesn't fix it).

Any help dearly appreciated.