Every keyboard key performs "Save as"

Hello folks,
I have just installed the latest version of K-Lite Codec Pack on a new PC. Now I am running in a quite peculiar error with Media Player Classic.

While it registers UI button clicks just fine, basically every key I press on my keyboard opens up the "Save as" window.
This happens with every video file I've tried so far. I've checked the settings, but there's nothing unusual there.

I've tried reinstalling K-Lite; the same problem occurs. I'd be grateful if anyone could offer me some insight in this error.

Something on your computer might be interfering with keyboard presses. I have no other idea what might cause this weird behavior.

Try rebooting the computer. Always a good thing to do in case of weirdness.

Thanks for pointing me in the right direction! I've found the offender.

The problem was with a text replacement program called Texter, that I usually keep running in the background. On my other PC Media Player Classic had no problems with it, so I never bothered looking there.