To address this issue,

First make a backup of the MetaBase:
Open IIS Manager
Right click on server->All Tasks->Backup/Restore Configuration...
Click Create Backup
Give the backup a name (e.g. 'Backup before fix')
Click OK, Close

Then enable direct Metabase Edit
Open IIS Manager
Right click on server and go to Properties
Check "Enable Direct Metabase Edit"
Click OK

Open the file C:\WINDOWS\SYSTEM32\INETSRV\METABASE.XML from Notepad.

Look for <IIsWebVirtualDir Location="/LM/W3SVC/1/ROOT/Microsoft-Server-ActiveSync"> and just below it, you
will see:

If like me you were too cheap to buy an expensive Verisign or similar SSL cert just to get Activesync working, knowing a cheap cert should do the same thing then p12imprt could be just what you are looking for.

No amount of installing the cert to personal or root stores on my mobile device (O2 XDA running windows mobile5) would help with getting activesync running (lots of 80072F17 errors) but the below did:

Get a copy of the cert from your actual server