Do you happen to have a spare keyboard and mouse to try on the system? If so, you can use that keyboard and mouse to determine whether or not the wireless combo is the source of the problem.

If the system works fine with another keyboard and mouse connected, the wireless combo itself may be the problem, and may need to be replaced.

When you last reformatted the drive, when was the exact point that the keyboard and mouse began experiencing problems again? Was it after the installation of any particular software and/or Microsoft Windows Updates?

Hi there, thank you for responding

Right now im using a really old keyboard, Dell Quietkey(...not that quiet...)
It works fine, alongside the very same cordless mouse that pairs up with the Logitech Cordless keyboard. Works fine with an old not-optical mouse. So it might be time to replace the cordless keyboard. But whats eating me is the fact that this has happend before (a year ago), just to work fine and the suddenly start to act weird again.

Well, after I reformatted it took a few days before it happend again. There where no hardware or/and software installation the last two days before it happend after the reformat.

So what do you think I should do? Get it replaced? Thats my thought, cause i've tried everything, spent hours upon hours searching for fixes and reading posts at forums.

Cody? You still around?

Yes, I would recommend having the keyboard replaced. As the keyboard likely does not have a separate part number, you will need to request replacement of the keyboard, mouse, and receiver module set.