yeah probably something wrong with the flashcard causing a short/power surge making the 3DS crash, i had a old R4 clone card that used to do something similar to the original NDS when inserted the console would immediately cut out, but occasionally it would work, cheapo cards aren't made with the most reliable of parts or build quality
honestly i would suggest you not trying it again in your 3DS as if its causing it to crap out it could potentially cause damage to the 3DS itself, try getting a replacement from wherever you bought it from