I can't change the Automatic Maintenance anymore. I guess i started it once manually and now its everrytime in progress. Pressing the stop button does nothing at all? Has anyone an idea how to force the stop or to get in the settings by a work around?
That is an odd issue. Do you have UAC set to at least the default level?
Have you already tried letting your computer sit running for a good amount of time to see if may finish running the maintenance and hopefully return back to normal?
If the above doesn't help, then you could first try a SFC /SCANNOW command first, and a system restore using a restore point (if available) dated before this issue started second.