I have consistently had this same problem since installing Office for Mac 2011.
I should have use the help line when it was free.

Problem: When writing an email in Outlook, I constantly see the spinning wheel in between each key stroke. This spinning wheel caused a latency of from 3 to 10 seconds between each key stroke. It's driving me crazy and I have all but abandoned Outlook for other email programs. I visited the Outlook 2011 Forum but with no solution. I have checked "rules" I have deleted all the caches using "Cocktail". It looks like Outlook is looking for something between or checking for something with each key stroke.