I think this might be related to the changes to using udev or DeviceKit. It started when I was running the beta versions of F12. Then it crept into Debian Sid. And my Arch Testing and Gentoo also suffer from the same.

What happens is that I'll be working along. Then when I press any key it is as if the SHIFT key is pressed. When I press CAPSLOCK, some of the keys react as they would normally. This never lasts for more than 5 minutes. And seems to happen infrequently. I say seems because there are the times I am at work and it could be that the same thing is happening only there is no one on the keyboard.

The reason I pick out udev/DeviceKit is that when it used to happen to F12 beta, the other distros had not yet made the move. So back then it was only a F12 issue. Now it is happening across the board. And only started recently.

Is it possible that the keyboard itself is malfunctioning? That would make more sense than it creeping into all distros; I don't think Sid updates udev that often.

i don't think so because it has happened with 2 different keyboards.

is it possible a BIOS setting is causing this behaviour?