Droid X switcihng from Charge to PC mode at random

[zeldarocks]

I recently got a Motorola Droid X to replace my failing Envy Touch as my upgrade period rolled around; after about three hours of use, I find that the battery has gotten quite low. I do what any sane inidividual would do and plug it into my computer; the Droid immediately begins to charge and directs me to the V-Cast website At this point it seems as if everything is going as it should, my phone is charging and I can use the USB as a data cable. Next thing I know, my X powers down, unsure of as to why, I plug it into the wall socket and realize that it had gone completely dead. Now, my question is, how is it that the Droid went from Charge Mode to PC Mode without any input on my part? Is my droid defective?