Let me know if you need any additional information.
Recently I started having a similar problem on my Samsung Series 9 laptop. I think this is actually a Windows 7 problem rather than a Lenovo problem. Look at these threads, for example:
I don't know what the cause is, but right now it seems like once I notice the problem I can clear it by tapping the CTRL key a few times.
Firstly, you can test whether the problem lies inside your Win 7 or not. Try different OS environments and see if the problem is still there.
If the OS is not to blame, the problem may lie in some low-level software (BIOS), or it's simply a hardware glitch. Here's something you can do:
Press the Ctrl before or during boot. Try both left/right. Do it several times and see if there's any noticeable difference.
Try a USB keyboard. If no difference, try un-plug the built-in keyboard.
Check your BIOS update again. Even if your tech has done it, something may go wrong.
Use something to display the input of Ctrl on your screen. Play with it for a while, see if you can notice any pattern. Is it always on once started? Does it keep switching between on and off? (I can't think of any handy tool for displaying key status under Win 7 at the moment. Maybe a game or something. Or you can code one yourself if you know how.)