Unfortunately, the fact that the progress bar reads Reading XMP is normal a red herring. That is, the hang is unrelated to reading XMP.
Try exporting directly through PPRO (by clicking the Export button in the Export Settings dialog) rather than queueing it to AME. Also, if you have Mercury Playback set to GPU Acceleration in PPRO, try switching it to Software Only.
Glad that workaround, umm, worked around the bug. I urge you to either post over on the AME forum and/or, better yet, submit a bug report against AME explaining that the app hung with Progress showing "Reading XMP" (i.e., before starting to encode) and that doing an in-process export got around the problem.