Canon camera error

When I started to to do some captures tonight the following message flashed across the screen for a brief time:

[Camera Thread] Canon: Error in PropID_SaveTo. Error: EDS_ERR_INVALID_HANDLE

I disconnected and reconnected the camera, power cycled it, quit and restarted SGP, and rebooted the PC, but it took several repeats of the above sequence to finally get the camera working again. Any idea what the real issue is and what I can do to avoid it in the future? This is the first time its happened, but I would like to avoid a repeat if there’s something I can do about it.