Shutdown 2000 Pro Twice To Shutdown Computer

This is weird. I have to go through the shutdown procedure twice, i.e., Start/Shut Down/Shut Down and click Ok, then Start/Shut Down/Shut Down and click Ok again. It will then shutdown properly. The same thing happens when I try to "Restart." After doing the first shutdown sequence, everything is normal. I can open programs, surf the web, etc. It's as if I never tried to shut it down at all. Only after the second shutdown procedure will it shutdown fully. One note: When I go through the first shutdown sequence, my taskbar pops up and the desktop is darkened. After clicking Ok, the taskbar autohides and my desktop returns to its normal color.I have only had this problem for the last month or two. Before that, all was fine. It's not critical since I can shut it down. It's just annoying to have to do it twice.I have Windows 2000 Pro, SP4, build 5.00.2195.