Sometimes when i boot windows vista it shows me a bsod and i don't know why.

LC Power 550W
Asus P5KPL-VM
Intel Core 2 Duo E6750
OCZ Kit 4GB (2x2GB) 800MHZ XTC Titanium
XFX Geforce 8800GTS 320MB
320GB Samsung SataII 16mb buffer
Windows Vista Ultimate x64

When i am able to boot into windows vista it says:

Problem signature:
Problem Event Name: BlueScreen
OS Version: 6.0.6001.2.1.0.256.1
Locale ID: 2070

Additional information about the problem:
BCCode: 6b
BCP1: FFFFFFFFC0000428
BCP2: 0000000000000003
BCP3: 0000000000000000
BCP4: 0000000000000000
OS Version: 6_0_6001
Service Pack: 1_0
Product: 256_1

Files that help describe the problem:
C:\Windows\Minidump\Mini122708-01.dmp
C:\Users\Diogo\AppData\Local\Temp\WER-78374-0.sysdata.xml
C:\Users\Diogo\AppData\Local\Temp\WERDD43.tmp.version.txt


There's the mini dump file, can someone analyse it please?
Thanks