Several application which should had accept and react to the F6 key seem to ignore it. Same applications accept the other function keys (F5, F7, etc.) performing their respective actions, as well as the Shift+F6 which also works fine as expected.
Because the Shift+F6 as well as Ctrl+F6, etc. work fine, I suspect this is not a hardware problem, but can't really be sure.
I don't think I've anything special on my Windows, or any program that intercepts F6, but again, cannot be sure.
How can I troubleshoot such a problem? How can I verify whether hardware/software? Any known program that intercepts F6?
Edit: Trying the Virtual On Screen Keyboard (as well as a different keyboard) yields same result (i.e. no result). This appears to be a software issue. Still no clue what it is.