Scenario: You've installed your "latest and greatest" software and the Autodesk Application Manager informs you that there are updates ready to install. You proceed to install the updates only to have them halt at a "Pending Installation" notice.
Cause: This is caused by having a space in the username of your Windows Account.
Solution: Login as an admin that doesn't have a space in the name and run the updates.
This issue is explained in detail in this Autodesk technical document: Application Manager stops at Pending Installation