Version : Outlook 2007 ( 12.0.6514.5000) SP2 MSO (12.0.6425.0000)
Part of Microsoft Office Ultimate 2007
Running on Windows XP Professional 2002 SP3

The problem:
Every 1 - 2 hours or so, it appears that Outlook freezes up spontaneously - with no external input.
It is determined that a crash has occurred when a message is selected from the Inbox list, (or any other subfolder) and the message list goes blank and an error message appears.
The error message indicates that the .pst file can not be read because it is locked by another user.
Here are some of the Application Event Viewer Messages:
Errors:
Failed to determine if the store is in the crawl scope (error=0x80070005).
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

Failed to get the Crawl Scope Manager with error=0x80070005.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Failed to determine if the store is in the crawl scope (error=0x80070005).
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Failed to get the Crawl Scope Manager with error=0x80070005.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Warnings:
Outlook Search has encountered an error and is temporarily disabling indexing for store C:\Documents and Settings\jashur.WITSAL\My Documents\Outlook Data Files\Jashur2009.pst (error=0x80040823).
Info:
The store C:\Documents and Settings\jashur.WITSAL\My Documents\Outlook Data Files\Jashur2009.pst is being reconciled with the indexer for the following reason: The store was last opened on a different machine
MS Office Diagnostics Message:
Office Diagnostics has determined that there is evidence of repeated problems.

I suspect that the Indexer is having a problem however there is reason to believe that perhaps there may be a plug-in that could be causing the problem.
Some plug-ins installed are :
PDF Converter 5.0 Outlook Add-in
Windows Search Email Indexer
OneNote Notes abuot Outlook Items
Microsoft VBA for Outlook Addin
Microsoft Outlook Mobile Service
Microsoft Office Groove Proxy for Outlook Add-in
Microsoft Office Sharepoint server Colleague Inport Add-in
Microsoft Echange Unified Messaging

Other relevant applications running on the PC are:
LogMeIn
ESET Antivirus
Quickbooks
Adobe Updater

Actions taken:
-Uninstalled & Re-installed Outlook
-Copied all messages to new .pst file and deleted the old .pst file.
-Deleted Expired Certificate for LogMeIn from Trusted Publishers list
-Rebuilt the indexing database but it didn't seem to work.
-Ran Registry Defense (Registry defragmenter/repair tool)

It looks a lot like the search indexer may be the culprit however I don't know what to do about it.

If anyone has any insight as to why it is crashing or how to effectively repair it, that would be great.
Thank you.