Vista - BSOD on Shutdown!

Hi, I am getting BSOD on shut down only. I disabled auto restart to get error message (thinking it may be a bad dll), only info is:

(S?) RQL_NOT_LESS_OR_EQUAL
(*?) **STOP:0X0000000A (0X0000000, 0X0000001B, 0X0000001, 0X8202924B)

When restarting I get the following error info:

Problem signature:
Problem Event Name: BlueScreen
OS Version: 6.0.6000.2.0.0.256.6
Locale ID: 5129
Additional information about the problem:
BCCode: a
BCP1: 00000000
BCP2: 0000001B
BCP3: 00000001
BCP4: 8202924B
OS Version: 6_0_6000
Service Pack: 0_0
Product: 256_1
Files that help describe the problem:
C:\Users\Colin\AppData\Local\Temp\WERE85B.tmp.version.txt
C:\Users\Colin\AppData\Local\Temp\WER-95628-0.sysdata.xml
C:\Users\Colin\AppData\Local\Temp\WERE85B.tmp.version.txt
Read our privacy statement:
Microsoft Online Crash Analysis

Other things I've tried
Used Onecare registry cleaner
Updated drivers incl BIOS and Graphics
Ran spyware, malware and virus checks
Defraged and ran Dell system checks (all OK)

Help please!