10.8.1 Problem - All Mail Stored 'On My Mac' Is Empty After Upgrading To 10.8.1

Hi,

I'm running a 15" retina MBP 2.3Ghz Quad Core i7. Just upgraded to 10.8.1 last night. Woke up this morning (GMT) and started up Mail.

Problem:

All of the mail stored 'On My Mac' has disappeared. That's literally thousands and thousands of very well organised emails relating to hundreds of different companies, projects, issues, people etc that are critical to the running of my business.

Everything in the inbox is still there.

Everything in flagged is still there.

Everything in draft is still there.

Everything in the sent items is still there.

Everything in junk is still there.

Everything stored 'On My Mac' has disappeared! 😮

The folder structure for 'On My Mac' is still intact but the folders are empty.

Main Work IMAP Account:

On further investigation, it seems that all of the emails for my main IMAP work email account have been moved to the 'Deleted Items' folder for that account. When I press 'Show' to reveal the list of bespoke folders for that account, there are now 5,702 emails in the 'Deleted Items' folder. It definitely contains emails that I have previously filed 'On My Mac'.

Also, bizarrely, the Junk E-mail folder for the main IMAP account has a count of 5,791 yet there are not 5,791 emails in it.

Other Email Accounts:

However, the 'On My Mac' section contained all my emails from my .Mac account and Hotmail etc and they have all disappeared as well, so this is not just limited to one specific IMAP account.

Other Info:

Strangely, any previous email that was managed by email rules, is still available and in the right folder... i.e. all my important emails are gone but for example, all the automated emails sent from LinkedIn that were managed by rules are in the right folder 'On My Mac' and pre-date last night's upgrade. It looks as if all the email not managed by rules (which is 99% of it) has been moved to Deleted Items in one big unsorted list which will take literally days to re-sort.

Please can someone help. This is a pretty horrific situation to wake up to.

Thanks,

Clown Guy

(not really laughing that much at the moment!)