Dell Vostro 410 sometimes won't shutdown - "System Has Recovered from

Hi all,

My computer sometimes doesn't shutdown properly (happens randomly). I have the problem already for some time but now I have the impression it is happening more often.

The problem: when I press shutdown the computer shuts down rather normal, first I see "logging off" the "computer shuts down". Then then screen switches off -> all normal, but the computer is still running, though with the fans are a little more silent. At that very moment I have the option to do a hard shutdown (which I don't really like...) or, the strange thing, when I wait 5 minutes the computer reboots automatically and I get the "System Has Recovered from a Serious Error" error message. It says there has been a bluescreen, which is not displayed on the screen, which stays black.

I have a Dell Vostro 410 with the standard Vista SP1 and I have installed a Sapphire HD 4830 & a new (very trustworthy) Corsair 500W PSU, because the standard 350W was insuficient. I'm pretty sure I already had the problem a few times with the old, standard ATI HD 3650.

I uploaded the dump files of the bluescreen: http://rapidshare.com/files/202877 [...] p.rar.html

Extra information over het probleem
BCCode: 9f
BCP1: 00000003
BCP2: 87BFA030
BCP3: 87BD9340
BCP4: 86776DE0
OS Version: 6_0_6001
Service Pack: 1_0
Product: 768_1
Servergegevens: 22f244b6-3de8-4c18-bd38-6e3228e88be4

Thanks in advance