Charging receptical not charging

Mine charges fine from seemingly any AC+USB source, until I let the battery die. *then*, it gets finicky and won't change (and reboots incessantly while plugged in if i try to turn it on). I just plugged it into the AC-USB plug that came with my ASUS Transformer, and now it is charging fine. I've lost track of the original AC-USB plug, so am unsure if that one works. If you can, suggest trying a different USB plug. The one that works for my dead-battery scenario is rated output at "5V ~ 2A or 15V ~ 1.2A" Good luck!