My Droid X's battery was totally dead. I however assumed otherwise because not only did i not get past the "M" logo, i didnt even see the "M". Its moments like those that make you cringe. I started to freak. I had a solid green led when i plugged it in but nothing else. I knew it wasnt totally bricked but i thought the worst. after a little searching i came across some other people that had the same problem. I didnt find anything here so i figured id share my stradegy.
1. Unplug phone.
2. Remove battery.
3. Remove SD card.
4. Put battery back in.
5. Plug phone into wall charger
6. Voila phone boots past "M" logo and into the charging screen.
Ive also seen some people saying that "cooling off the battery" works before putting it back in. Also pressing the power button without the battery in. Hope someone finds this useful.