i got one of these......no problems as such...has played everything great......
when i first got it, it wouldnt play anything which had more than 4 reference frames i think it was and like yours got a blocky unplayable film.....this was rectified with a firmware update....im only using official release firmware and mine seems fine.....
some encoders are coding there media with very high reference frames when there is no need to.....check out the firmware release notes and see if theres anything in there......
also might be worth a look at pic settings.......i think 24fps doesnt work well either even though ive never tried it.....i use 1080p at 60hz and everything plays fine....even blu ray mt2s files.....could also be the media you have got.....