Just thinking out loud here...
As the registry files are saved to the hard drive, ( I know they are loaded into memory when Windows starts), is it possible that NU is trying to access the file on the hard drive? If this is the case, it is possible there is some physical problem with the location of those files on the disc? Maybe a disc check would be in order, it cannot hurt.
To check your hard disk, click on the Windows Start button. In the search box type CMD. Right click on cmd.exe and click on run as administrator. In the command prompt type "chkdsk c: /r" without the quotes. A message will come up asking if you want to check the disk on the next restart. Answer 'Y'. Reboot and the check disk will run before Windows starts up. This check will check the file system as well as the physical disk surface. This scan can take a long time, depending on the size of your hard drive.
Whatever you find out will be useful to someone. It may be one specific program or utility you have that may be uncommon. If even one other user has that same program it could help them.