I have noticed that since my OTA update to 2.2 last week that some of my mp4 videos will no longer play. Strangely, some of the mp4 files that I had will play. The Gallery preview shows a blank box and if I click on it I get a "Sorry, this video cannot be played." These same videos played fine under 2.1. Does anyone know that changed between 2.1 and 2.2 to cause some videos to play while others will not? It seems strange to me that they would take a function that was built into the system and break it for a system update. As a side note, I downloaded RockPlayer (ARMv7) from the Market and it will play all my mp4's plus some other formats that 2.1 would not play.