Exporting mix files with closed captions.

I'm trying to export files with closed caption using (.mxf / EX 1080 60i / with side care .ssc) via Media Encoder.  Once I hit "Queue" in Premiere, Media Encoder opens and it appears to load, then it just hangs.  It says its exporting but nothing happens.  I have to quite the export and end up having to export the file dirrectly from the Premiere timeline which then means I cant do anything else in Premiere till the file export is complete.  Anyone else have this issue?  I can replicate it on multiple Macs and a PC.