64-bit Vista Ultimate hangs on "Restart"

[-Kestrel-]

Invariably of late (last week or two), when Vista has to be restarted (e.g., OS patch, of which there have been several lately, or after installing an app), I get the "Starting Windows" graphic, then a blank screen. Shutting down and rebooting always works fine.

Any suggestions on where/how to troubleshoot this?

Asus A8N-E Rev. 2
Athlon 64 X2 4200+ (Manchester)
4x1GB Crucial D400
Leadtek GeForce 8800GTX
2xHitachi 160GB SATA300
LG External LightScribe DVD-RW/DVD-RAM