This is a composite reply.
Juhaz and qazokm1, a disclaimer: I don't know anything more than what I have posted, and all of that came from the Apple Support people. I am just an end user like you, with a few years experience with Macs.
Juhaz--are you sure you got all the com.apple.windowserver.xxxx.plist.xxx files out, including from the ByHost directory under /youruser/library/preferences/ByHost? You have to go to all these directories and can't just do a search in Finder or Spotlight. But maybe there's something else going on with your MBP 17-inch 2010. If you still have AppleCare, you might have to call them. They should have something about this issue in their database by now.
Again, my understanding is that you can delete any plist file you want and nothing bad will happen. These files are created every time a new process is run, and changed as necessary, and don't even exist before that process is run for the first time. They are sort of like a cache memory for processes, and deleting them may mean, at most, that you will be asked to set up preferences in some processes the next time they are run. For example, if you deletd the plist files for your wi-fi, your wifi would still work, but you might not have a list of the various previously used wifi networks and would have to set them up again. It would cost you some time but nothing else. In any case, you can hold onto the plist files in Trash and put them back again if you want to do so.
