It's most likely a driver issue, which can be fixed by reinstalling the keyboard's software package. If the keyboard came with the computer, check the manufacturer's website for the download.
Also, if possible, check your Windows Update log and let us know what update (KBxxxxx) caused the problem. A small update like that should not take that long, and any update certainly shouldn't cause such an issue.
I decided to restart my computer today. While it was shutting down, it began installing an update. No big deal. However, after 20 minutes, I got suspicious. After 45 minutes, I made the tough decision to shut down the PC. In hindsight, maybe it was a mistake, but I dont think I had much of a choice. I later found that the update was under 1MB in size... nothing major. So I have no idea why it took 45 minutes???? Regardless, I booted back up, and everything was screwed. Long story short, I ran a system restore, and rolled back to yesterday, and then installed any new updates. Mostly everything is back to working as usual... thanks to me keeping good backups of everything. Only problem left is: now my keyboard doesnt work right. Half my keys dont work, including both "enter keys", the numbers below the Function keys, and the arrow keys. Hence, the TERRIBLE formatting of this message. This is a PC with a USB keyboard. I have tried unplugging it, and plugging it back in, and several restarts. I dont know whats wrong with it. Any ideas of what to do?