08-09-2014 11:05 AM
The Canon Service Dept seems satisfied that I have conducted all the diagnostics on this problem and have recommended sending out the camera for warranty repair. Thanks again for your help.
08-20-2014 05:20 PM
As an update, I just received my T3i back from the Canon USA Factory Service Center. As I suspected the SD memory cards were fine. Service details stated that the SD circuit board was defective and malfunctioning; and was unreliably recognizing any memory cards. The SD circuit board was replaced at no charge.