Animal Crossing City Folk error

FYI for anyone who has a similar issue:  I tried to play Animal Crossing City Folk on the Wii and after opening up my game, it suddenly gave the Wii error message “An error has occurred”, along with telling me to hit Eject, remove the disc, and turn the power off.  I was able to eject, but the power button didn’t work, nor did reset.  I had to unplug the cable from the back.  When I tried the disc again, it wouldn’t load my game, it just showed the schoolbus icon in the corner for ‘loading’.  The disc looked fine, and when I tried playing Super Paper Mario, another Wii game, it played fine.  (Thank goodness for that:  I’ve had my disc drive replaced once already and don’t want to again.)  I then noticed that I had an SD card in the slot and remembered I had taken a photo and saved it to the SD card the other day in City Folk.  I ejected that, reinserted City Folk, and it loaded my game fine.  Resetti came by and gave me the run-down about not hitting reset, blah blah, but everything appears fine now.  Maybe a fluke, but maybe starting the game with an SD card in the slot is problematic.