I hate to suggest the obvious, but: Both the operations that are causing problems (image deletion and card formatting) are destructive operations. That being so, the dialog that comes up requiring you to press the 'OK' button has the default action set to cancel out of the whole operation. If you just go ahead and press 'OK', nothing is done; you have to explicitly move the selected action to the 'Yes - go ahead and do this' line.
It's easy enough for a user unfamiliar with the camera to misinterpret the display, and to the think that the default action if the 'OK' button is pressed will be to proceed. So, Shel - are you just pressing that 'OK' button, or are you changing the selected action first?
