(2 things, and I don't know if they are connected!)
FIRST: I have discovered 2 shortcuts in my 'Games' Start Button folder. One is SimCity and the other one is a Steam game:Dark Messiah, Might and Magic: Single player. I don't know anything about them. THEY WON'T DELETE. I have even tried going into Safe Mode to delete them but no luck. The r/click doesn't have the delete option. Dragging them to the Recycle bin justs make them reform again. There is no reference in my Registry of these, and I have no programs of these names in my Program Files folder, so I presume they have been installed to play over the Internet. How do I get rid of them?
SECOND: About once a day, without any warning, my menus and my slide bars go very unstable. On the menus, a bar runs up and down the menu if you try to click on it, and it cannot be controlled by the mouse. The slide bars just go up and down of their own free will. WEIRD. I have to reboot to get control of them again.
Windows Defender, Spybot & C, AdAware and AVG Virus protection ALL state that I have no problems with my PC and everything is running normally.
50% success, found one file called MAXIS which I found produced the SimCity. Deleted folder and the shortcut disappeared from the Games folder. Updated graphics driver but that made no difference to the unstable menus and slidebars. All checks I do on PC still report I have no problems.
Since your scans come up clean for nasties I am just wondering if the problem with random scrolling may be mouse or keyboard related you could try updating your drivers or using a different mouse and keyboard.