Vista SP2 Causes Shutdown Problem?

[#1]

Hi,
Vista Business edition on my HP DC7800, with SP1 - no problems for ages. Upgraded to SP2 this morning, and now when I specify a SHUTDOWN, instead it does a Shutdown-then-apparent-restart - but it then tells me it had a BlueSceen (tho I never see it) - so I'm assuming the restart is an auto-restart-after-bluescreen. Any clues as to what is going adrift?
Jack

[#2]

Disable automatic restart and you may get more info.
There are definitely changes to the power management so that may be related. Oddly enough my system (also Vista Business) used to "hang" on a shutdown or restart in the very final stage, requiring manual intervention. Now with SP2 it behaves correctly.

[#3]

Yes, with auto-restart disabled, the blue screen does appear (after exactly (?) 100 seconds), giving the same codes as given  in the after-restart popup: (which is)
Problem signature:
  Problem Event Name: BlueScreen
  OS Version: 6.0.6002.2.2.0.256.6
  Locale ID: 2057
Additional information about the problem:
  BCCode: 1000008e                                          (this is always the same value)
  BCP1: C0000005                                          (so is this....then the rest do vary somewhat)
  BCP2: 81EDE033
  BCP3: C5CCDA74
  BCP4: 00000000
  OS Version: 6_0_6002
  Service Pack: 2_0
  Product: 256_1
Files that help describe the problem:
  C:\WINDOWS\Minidump\Mini052909-12.dmp
  C:\Users\jack\AppData\Local\Temp\WER-88592-0.sysdata.xml
  C:\Users\jack\AppData\Local\Temp\WERD69F.tmp.version.txt

There's nothing useful in the event logs, and I've tried not runing my Antivirus, and binning all network connections beforehand. The shutdown process used to take between 2 and 3 minutes - now it takes 100 secs (so there's a bonus!).

[#4]

After I got no help from Microsoft or HP, I tried the HP Forum, and got a kind offer from a contributor to check-out the minidump file. That proved to point to a process called safeboot.sys, which seemed to be associated with the HP Protect Tools suite which came installed at delivery. Since I make no use of them (as far as I know), I uninstalled all their components, and that cured the bluescreen problem.
However, since I'd already been prompted to review all drivers, I'm continuing to review/update all drivers via DriverMax (a free driver check/update utility) - just in case!

[#5]

Update Info:
Curiosity got the better of me! - I reinstalled Vista from scratch on the PC, applied SP1 and then SP2, whilst checking performance/startup/shutdown at each stage. Then applied all current MS Updates.  I experienced none of the previous problems, and shutdown now takes 25-30 secs - much better.