So the title describes the problem, but I'll give more information.
It started when I got a micro SD card; files would not fully transfer onto the card, and the progress would stop halfway. This was in Kies, but when I contacted technical support, I was told to try transferring the same files using windows explorer via My Computer. This yeiled the same problem, so I assumed it was a problem with the SD card. After changing the SD card, the problem persisted.
Now, at the same time, I noticed that my phone was constantly saying "USB connected" even when it was not. In this state, some times the phone would turn off. Pressing the power button would have no effect but to show a "charging" symbol of the phone (looks like a circle made up of small lines pointing outwards). The only way to turn the phone back on in this state is to plug it in, take the battery out, and put it back in again. The phone would return to the broken state once unplugged.
Can someone PLEASE PLEASE help?!