[Tom Kerr]

Ran into the same error 19 and had been using Encore CS5 for years with no difficulty.
The MPEG2 Blu-ray export from Premiere was defaulting to PAL format. Specifying NTSC in the export video settings fixed the primary video stream error in Encore as well as problems playing in standard Blu-Ray players (it would exit the DVD and return to the player menu). Hope this helps others still using Encore.