Weird keyboard driver issues?

I've been running a Sager NP9130 for almost two years now, with very few issues.

However, I've encountered a really frustrating bug that I've had a hard time trying to resolve. I use the laptop with an external keyboard (microsoft sidewinder x4), and up until yesterday, everything was working perfectly. As of yesterday, the tab key became stuck, and windows was registering a key press every ~.5 seconds. I've tried quite a few things to resolve it. I have figured out that this occurs even when the external keyboard is disconnected. I've inspected the tab key, and there does not appear to be any contamination or damage that would short it. I've figured out that uninstalling the laptop keyboard driver (by uninstalling the "HID device" under "Keyboard" in device manager) does resolve the issue, but as soon as windows re-installs the device, the issue reappears.

Lastly, I physically disconnected the laptop keyboard ribbon. Even with both keyboards disconnected, Windows still registers a TAB keypress every .5 seconds. Even with the keyboard disconnected, Windows still re-installs the device driver eventually, causing the issue to reoccur.

I'm at the end of my rope with this issue, as there's nothing else I can think of. Anyone else ever encounter a similar issue, or have any other suggestions? Any help would be greatly appreciated.

 

Do you have a image for Windows that you can restore to? If not try boot your system from a live CD/DVD or USB with a Linux distro (see try before you install) here Download Ubuntu Desktop | Download | Ubuntu and test. This will rule out a windows bug (I assume you are running 7 ??). Please let us know!

 

It could be a faulty keyboard controller chip. Has there ever been any spill damage to the board? Liquid damage can cause erratic behavior in circuits (when it doesn't ruin them altogether).

 

Aha! I just discovered the issue. Turns out it has to do with my Logitech G700 mouse, which has a few rarely-used buttons. One of these is apparently mapped to Tab under a specific default macro setting, and this button was jammed closed, causing it to send a Tab signal erratically. However, all my keyboard monitoring software could only detect that this input came from a keyboard, not from the mouse.

Every time I killed the keyboard driver, my mouse could no longer use the macro properly, causing the issue to disappear.

Thank you all for the support.... turns out it's much simpler and dumber than I expected.

 

Thanks for the follow up!