Outlook not opening - pst corrupt

I opened up my MS Outlook 2005 and the following error popped up, and then shutdown Outlook:

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Microsoft Office Outlook Offline Folders
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'Microsoft Office Outlook' exited without properly closing your Outlook data file 'C:\...\outlook.ost'. 'Microsoft Office Outlook' must be restarted. If this error message recurs, contact support for 'Microsoft Office Outlook' for assistance.
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OK
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Solution was to:

1. Run Start > Microsoft Office > Microsoft Office Tools > Microsoft Office Diagnostics

Helpful links:

http://www.fixya.com/support/t1163842-cannot_open_outlook_2007
http://office.microsoft.com/en-gb/downloads/default.aspx (Office Update)