Strange StickyKeys or CTRL plus key type of problem

One of my PC's running Windows 7 Pro has just suddenly started acting very strangely.

Basically when I press the "r" key, the run dialog box opens. The same issue happens when I press other keys on my keyboard - it is as if I am pressing the CTRL-key plus the other key. This happened suddenly without warning and I have been unable to get rid of it.

I have tried the following (none of which made any difference):
1. Explicitly turned off stickykeys in the ease-of-use/acessability options. [they weren't switched on, but I unticked everything anyway]
2. Tried a different USB keyboard
3. Tried the on-screen keybaord
4. Tried booting in safe Mode and using 1-3 above.
5. Edited the registry (which was fun when you can't enter "r" into the search box as run immediately opens), and changing the following:
HKEY_CURRENT_USER\Control Panel\Accessibility\StickyKeys - changed Flag to 506 (also tried 26)
HKEY_CURRENT_USER\Control Panel\Accessibility\Keyboard Response - changed Flag to 122
HKEY_CURRENT_USER\Control Panel\Accessibility\ToggleKeys - changed Flag to 58

[I also changed the above keys in HKEY_USERS\Default\ControlPanel\Accessibility]

6. Reverted to an earlier image of my C: drive from earlier this month and made the above changes to that restored image.
7. Run an anti-virus check using Avast (which normally runs in the background anyway) - it came up clean.

None of it made any difference - they keys are still behaving strangely.

Can anybody suggest what is causing this issue and how I can resolve it?
Is it software or hardware (even BIOS) related???

I've tried all that I could think of, so any helpful suggestions greatly appreciated.

Hi

to me it sounds like the keyboard controller is faulty, since it does it with another keyboard and on screen keyboard. have you tried running a live disk like ubuntu to verify not a software issue?

I have managed to resolve the issue - but to be honest I am not sure how!

In addition to the steps outlined in my original post I tried the following:
* Booted up in safe mode - made not difference
* Rebooted the BIOS by taking out and then reinstalling the BIOS battery - made no difference
* Ran various rootkit scans (Kapersky tdsskiller and Malwarebytes Anti-Rootkit beta) - both came up clean; keyboards still didn't work

* Booted from a Ubuntu distro on a USB - all of the USB keyboards I used worked fine! However on rebooting into Windows I was getting the same issue. Pressing "r" caused the Run dialog to appear, "e" caused Explorer to open and so on - as if the CTRL key was being pressed at the same time.
* I tried the keyboard in different USB ports - still not working properly.

So I rebooted using a PS2 keyboard (luckily my motherboard - a Gigabyte X58A-UD3R - had PS2 ports).....
and the keyboard worked!

I then reinserted the original USB keyboard - and it worked as well! As did the other USB keyboard that I had tried.

Now I have no idea what the problem was or why putting in a keyboard into the PS2 port worked and cleared it all up; but it did. I reinstalled my most recent image of my C: drive (as I had reverted to an older one in case something had recently changed in my system) - and the keyboard works OK.

So somehow the problem was solved!

I will post again if the issue reappears - but for the moment, keep fingers crossed.

Hope it stays that way