Last night I fell asleep listening to music and I realized this morning I pretty much drained my battery. I didn't have time to plug my phone in a wall charger before I left for work and I'm trying to charge it using USB plugged directly into a USB port. The phone doesn't seem to be responding to anything. In the past, when my battery was drained, the phone at least turned on to indicate a charge. Today, there is nothing. Is this normal? I understand it takes longer to charge via USB so do I just have to wait that much longer to indicate a charge? Or do I have a bigger problem?