I am running Windows 7 and began experiencing keyboard lag in most applications, and it seems to be getting worse. Certain websites are the worst - on some, I can type a sentence, take my hands off the keyboard, and watch the characters continue to appear on the screen for several seconds. Others are not as bad, but still noticeable and annoying. I just started noticing it in non-browser applications (e.g. Outlook) as well.

I've disabled all extensions in Firefox, rebooted my machine, and that did nothing. There is nothing using much memory or cpu cycles, even when the lag is occurring.

This is a machine at work with very strict controls over what can be installed, so the chances of any kind of malware are very slim. I don't believe anything as been installed since before the problem started.

What could be causing this, and/or what can I do to debug?