Se con SharePoint 2010 ti capita questo errore:

Log Name: Application
Source: VSS
Date: 02/01/2013 15:34:34
Event ID: 8193
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Computer: SP03.sgart.local
Description:
Volume Shadow Copy Service error: Unexpected error calling routine RegOpenKeyExW(-2147483646,SYSTEM\CurrentControlSet\Services\VSS\Diag,...). hr = 0x80070005, Access is denied.
.

Operation:
Initializing Writer

Context:
Writer Class Id: {0ff1ce14-0201-0000-0000-000000000000}
Writer Name: OSearch14 VSS Writer
Writer Instance ID: {75c4796a-7d13-4170-83ca-9a59bdeaf5cd}
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/200...events/event ">
<System>
<Provider Name="VSS" />
<EventID Qualifiers="0">8193</EventID>
<Level>2</Level>
<Task>0</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2013-01-02T14:34:34.000000000Z" />
<EventRecordID>4781</EventRecordID>
<Channel>Application</Channel>
<Computer>SP03.sgart.local</Computer>
<Security />
</System>
<EventData>
<Data>RegOpenKeyExW(-2147483646,SYSTEM\CurrentControlSet\Services\VSS\Diag,...)</Data>
<Data>0x80070005, Access is denied.
</Data>
<Data>

Operation:
Initializing Writer

Context:
Writer Class Id: {0ff1ce14-0201-0000-0000-000000000000}
Writer Name: OSearch14 VSS Writer
Writer Instance ID: {75c4796a-7d13-4170-83ca-9a59bdeaf5cd}</Data>
<Binary>2D20436F64653A20 ... 20202020</Binary>
</EventData>
</Event>

è perche alla chiave
HKLM\SYSTEM\CurrentControlSet\Services\VSS\Diag 
manca il permesso di Full Control all'utente con cui gira il servizio SharePoint Server Search 14 (OSearch14).
Apri regedit e dai il permesso all'utente, poi riavvia il servizio.