Truthfully, I haven't played much of anything other than flash and youtube vids through my DX so far. I have been dicking around with Dropbox...which I find really intriquing btw...so cool and easy. Well, I moved a short .mpg to a folder in dropbox and it showed up immediately. Clicked on it through my phone and it did the quick download to the phone, asked me what I would like to use to watch it, Mixzing or the stock player...I chose stock. Got the "file cannot be displayed or played" failure. So I chose Mixzing instead. Got the same failure.
So...is .mpg a bad format? I rebooted, same thing.
***edit, it wont play WMV either***