You cannot download Microsoft Office for Mac 2011 updates after you install Microsoft AutoUpdate 3.0.5. Additionally, you notice that lots of memory is consumed when AutoUpdate 3.0.5 runs.
To resolve this problem, install Microsoft AutoUpdate 3.0.6.
How to obtain the update
Microsoft Download CenterThis update is available for download and installation from the Microsoft Download Center:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Microsoft AutoUpdate for Mac is provided together with Office. It automatically keeps Microsoft software up-to-date. To use AutoUpdate, start a Microsoft Office program, and then click Check for Updates on the Help menu.