S2Member, Cloudfront and JWPlayer

Just wondering if anyone else has/had this problem:
I applied all the instructions from Jason to set up Amazon S3/Cloudfront and JWPlayer. All has gone well, with the RTMP and Web distros set up via S2Member. Here’s my problem: In trying to run a test, the JWPlayer loads, and then the video loads, but stops after just 5-10 seconds, then the player freezes on a black screen. On some occasions, the video runs to the end, but most of the time it stops after 5-10 seconds.
Any others experience this?