This just started today. I'm thinking it might be just because the battery is run down but I'm in the red, and I'm charging off of a USB that has always charged fine before (though not quite as fast as my wall charger). I don't have access to my wall charger until tomorrow and I'm trying to charge it up now, but it won't take a charge when the phone is on. When I turn the phone off, it takes charge for about 5 minutes then turns on. When it turns on, the charge light goes off and it tells me to connect to the charger. I've tried unplugging the cable and plugging it back in and the light stays off. As far as I always knew the charge was strictly hardware based so why would it only take a charge while the phone is off?
Edit: After some further experimentation I was able to get it to recognize USB for about 5-10 minutes, enough time to get the charge up by about 5%, but then it immediately shut back off and I'm back where I started. I have no idea what I did and I haven't been able to repeat it.
Edit 2: So after unplugs, restarts, and the same nonsense repeated about 50 times it finally took a charge. I had the SD card out so I don't know if that helped. Promptly after doing the restart I needed to do to put the SD card back in, the phone began not taking a charge again. In fact, when it is powered up, it won't recognize the USB at all, but the instant it's off the charge light come son (of course due to motorola's stupid move to make the phone start up when plugged in this doesn't last long).