I've just heard of another similar complaint but with a T43 controller. I'm still investigating, but it is possibly that the file that causes the $0502 error is an old file and does not contain enough (or incorrect) information in the meta data section of the *.ctd file. Specifically the OS and/or Stream settings. Can you please send me (paul@efilive.com) the file that works and the file that does not work and I'll check.
Regards
Paul