>I've run into this when an app - VFP or .NET- is not running, but the VFP or .NET IDE that ran the app is still open. When I close the IDE the issue goes away.

In SSMS, sometimes, an open query window would generate the same situation. IAC, just to sure, whenever I need to restore, I close everything. Then, sometimes, I even have to restart SSMS. When this is not enough, I stop IIS, which might still has some live links to previous database queries. At the very end, a restart of the service. However, recently, not of them was successfull. Yesterday, the switch to single user was the only way to restore.