I have a customer with an Office365 Small Business Premium subscription.  One of the users has a MacBook Pro and iMac both running Mountain Lion with Office 2011 fully patched.  When running Outlook, we see extremely high CPU usage by the Outlook process - it's averaging about 95%, which in turn causes poor performance on the MacBook/iMac in general - the spinning beachball repeatedly pops up rendering the MacBook unusable.  I've been through a lot of troubleshooting on this to no avail.  Here's what I've done so far:

• Reinstalled Office
• Created a new user profile
• Rebuilt the Outlook identity
• Rebuilt the Outlook database as per http://support.microsoft.com/kb/2360509
• Cleared out Deleted Items as per http://answers.microsoft.com/en-us/mac/forum/macoffice2011-macoutlook/mac-outlook-1412-cpu-runs-very-high-since-install/82b8671b-f186-418e-b751-a5d6321f0f07
• Reindexed Spotlight
• Disabled autodiscover in AppleScript as per http://www.officeformachelp.com/outlook/exchange/autodiscover/
• Reduced the number of subfolders/items in "important folders"
• Disabled Sync Services
• Set Outlook to download headers only

What is curious is that I've just setup a brand new iMac for this user and for approximately four hours after connecting to Office 365 the iMac ran  perfectly well, then boom - I've got exactly the same problem.  The only other apps that were installed were Evernote and Dropbox.

Does anyone have any suggestions on troubleshooting this further?