[George Snow] "He transcoded the DSLR footage to ProRes 422 (HQ). Which again does not play. "
[George Snow] "Since I've transcoded files that were already transcoded, have I lost any quality? Is this something that shouldn't be done? "
Whenever you transcode to a compressed format there is some quality lost, although in this case I wouldn't be concerned.
What you have to fix is the issue of the Prores HQ not working on your system. Should do it.
Rafael
http://www.nagavideo.com