Hi Frisco!
This happened to me a few months ago, so I think I know what you could do.
This sometimes happens when system files are corrupted, so we need to get those system files back to what they were before the problems. In my case a software corrupted the system files. Did you install or uninstall any software latelly?
Anyway, all you have to do is to do a system restore. A tutorial can be found here:
System Restore
Try that and don't forget to scan for malware or viruses beforehand.
Cheers,
Fire Cat