Outlook stuck on ‘determining changes’ and won’t download email

I'm using Outlook for Mac 2011 14.4.2 with latest updates installed on OS X 10.9.2

For several days now I have been unable to access email in Outlook.  Everytime I open outlook and check mail it says "determining changes" and cycles through inbox, trash, sent, drafts etc. It spends ages doing this but ultimately no mail is received at all.

I can send mail though (?!)

My account is setup using IMAP, using the setting suggested by my email host.

I have tried deleting and reinstalling the email account in Outlook, rebuilding the identity, running a new identity, logging into the computer with a different user account, deleting email from the folders on the server (via webmail) but all to no avail.  It is driving me insane.

The volume of mail on the server (accessible via webmail interface) is small with only 544 emails in the inbox (265 MB) total and 1204 email in the sent folder (260 MB in total).

Any help would be gratefully received as I am paralysed here.

Many thanks