Digital files do not degrade. Period! You can take that to the bank.
Computer hardware can degrade, and that is what the others are suggesting to you. I'd first make a backup of your KMA files to another hard drive or CD/DVDROM discs, if you haven't already.
Are you noticing any strange video behavior? If so, your graphics card may be the cause as was suggested. If other programs show their video images without any distortions, then its probably not the video card.
Next, run a disc test to see if there are any errors on your hard drive. It it shows up a significant number of bad sectors (the disc test SW may make recommendations), you are running on borrowed time. Consider replacing your hard drive.
If you do this, you may need to contact us to get Hoster to reinstall. We'll be glad to help.