beestea,
Welcome to the forums! :welcome_s
Yes, you both have found a common, painful, but intermittent defect with the HR20. The unwatchable recording which comes in two flavors: the ones that self-delete on a reboot and the ones that actually can be played with some patience and fast forwarding (usually).
If the recording survives a reboot, you usually can get it to play by starting it and pressing FF or slip until the screen displays the show. Then you usually have to rewind to the start of the episode again.
Some people have reported that immediately after pressing play, pressing the 6 second jump back button will also work sometimes.
I sure hope that directv will have these problems fixed very soon. A DVR that can't be relied upon isn't much of a DVR. As much as I like some features of the HR20, I can't be happy to have had 3 of my units lockup this past week. Had I been on vacation, they would have done nothing for me.
Good luck,
Tom