Previous to the update, I was running the 20130218 FW and the 4 SD, 30 minute recordings previously played fine. This was on a 32G USB stick.
Normally I do not keep archived and delete after watching or soon after. I recorded another episode last night and is OK.
I went back and checked some previously recorded HD material and some 60m shows and one movie on my USB EHD and all were intact.
Perhaps was an isolated case here with the USB flash drive and time for a reformat. I don't recall exactly what others found with the testing they were doing with this issue or if it was ever really explained. But I remember something about missing or duplicated data packets which is outside of my area of expertise. The microHD just plays a blue screen that appears to be fast forwarding, the index numbers or whatever they represent on the playback info screen appear to jump all over. I'm not sure how to interpret those values.