Windows 7 Outlook issue: "ost is in use and cannot be accessed".

I got to work early today, ready to get to work, and was greeted with this cheery note from my Windows 7 box when opening Outlook:

"The file C:\Users\username\AppData\Local\Microsoft\Outlook\username.ost is in use and cannot be accessed. Close any application that is using this file, and then try again. You might need to restart your computer."

Restarting the box did not help. I had to open the "Windows Task Manager" (Ctrl-Shift-Esc), select "Lync.exe" and kill it (you might also need to kill "Communicator", "ucmapi", or "Outlook" itself). Then Outlook was happy and I could start my day.

This morning's ambush reminds me of Cato hiding in wait for Inspector Clouseau to return so Cato can attack him, just to keep Clouseau sharp.