San Disk Miscro SD 32gb and Quicktime

Hello I have  a problem. I am trying to upload mp4 movies onto my SanDisk. The movies are only 1 Gb max, and when I add the first one it will play from the card, but any one I add afterwards wont play. The message I get is : The document “.m4v” could not be opened. The movie’s file format isn’t recognized.   The problem isn’t the movie because no matter what movie I transfer to the card first, it will play. The format is FAT32, are these cards not able to hold media this large? What can I do so I can add more movies and watch them with no problem? Thank you for your time. BTW I have an iMac if that makes a difference.