For instance I've had repeated instances of this with Norton, but a recent discussion died when the member didn't share details.
Try this. Use HIJACKTHIS to get a snapshot of what's running prior to a hung shutdown and use that to compare to when it does work.
Microsoft Windows XP
service Pack 2
CPU 230 GHz
2.29 GHz, 248 MB of Ram
When I want to shut off my computer, I get the error message, DDE server window not responding. I know when it's going to happen, I get the arrow/hourglass icon when I log on. I've looked all over the internet for this answer, and most of them don't make sense, or tell you to mess with your registry, which I'm afraid to do.