Outlook 2011 not receiving mails

For some time now i have been experiencing  issues with Outlook 2011, in that i cannot reliably receive mail.

I have two accounts set up one is a @me.com the other is a gmail account and the issue i get is across both accounts.

In attempts to rectify the issue i have:-

1. Rebuilt the database
2. Created a new identity

But these two actions does not appear to resolve the problem....

I am operating at the latest version of OSX and Office is at 14.4.1

Any advice will be very gratefully received.

Thank You.

John