Windows Explorer Stackhash error in windows vista ultimate 32 bit

Hello. I Installed windows vista last night on my Dell Latitude D620 (dont
know if this helps). I upgraded from windows xp proffesional. Scince then I
have been having a problem. I tried to acess control panel to change
something and I got the:
Restart Windows explorer or search online then restart it. Firstly I clicked
online and nothing came up, it just restarted explorer...

Can any one please help. Here is more what it says:

Problem signature:
Problem Event Name: APPCRASH
Application Name: Explorer.EXE
Application Version: 6.0.6000.16386
Application Timestamp: 4549b091
Fault Module Name: StackHash_3ee5
Fault Module Version: 6.0.6000.16386
Fault Module Timestamp: 4549bdc9
Exception Code: c0000374
Exception Offset: 000af1c9
OS Version: 6.0.6000.2.0.0.256.1
Locale ID: 2057
Additional Information 1: 3ee5
Additional Information 2: 9a6f3ad485f09e2480d495f1299fb930
Additional Information 3: b5d8
Additional Information 4: 5e186f3fbdad3747803a5bf01b9ace45

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Thanks.