For best results you need a Class 4 or better SD card... Class 2's dont work well with 720p video

 

mine the same as times and I've read other complain, in fact original reviews of the phone do say this, although it doesn't always stagger and I've a new re-formatted class 4 card.

 

Just got my Desire S, great phone, but the recorded vidoes (720p) wont play. Just black screen and sound. When connected to PC movie plays gr8 on the PC.

Here's my solution to the problem:
1. Switch phone off
2. Open phone
3. Remove battery and uSD-card
4. Re-insertt uSDcard and battery
5. Start phone
6. Voila, playback works

Note: Just switch off and on / restart phone will not work.