Client window - Update already in progress

[j-gray 35]

Running the latest OS X client and agent. Several times over the past two days this warning dialog has popped up. The regular automatic update is set to run every hour. I'm guessing that the update task must be running longer than an hour, which shouldn't be the case.

The client scheduler shows the last run time as the time the error message popped up. The client Event Log is completely empty.

What's the best way to determine what's going on here?