Heck man, my Atrix HD just ran into the EXACT same problem. Phone doesn't turn on except when plugged into a charger, and even then it just keeps bootlooping. Also doesn't boot into recovery either (even though it has Philz CWM on it) only AP Fastboot.
Thing is, it was working perfectly fine, with a full charge, just minutes before. I sent a text with the battery full, then went to play BF3 for half an hour later and phone was off. Tried hard reset, didn't work. Tried the usual charger I use for it (Galaxy Nexus charger), nothing. Tried a higher amp charger (BlackBerry PlayBook charger, 2A) and just green light + bootloop.
Galaxy S4 I337M Blue - Stock 4.4.2, AWS modded
Nexus 5 16GB White - CM11 Snapshot M8
Huawei Ascend D1 Quad XL - Stock rooted 4.0.4