I've had this issue with both my new E4GT and my old Evo 4G. It seems to happen with certain non-OEM charging USB 'blocks' and/or cables. With the E4GT, using the charger included with it has solved the problem, which I narrowed down to some USB wall charging blocks (e.g. looks like the iPhone USB wall charging block but black) that I bought from eBay (but that worked fine with my Evo 4G). Non-OEM micro USB cables that I've used seem to be fine though.
In my experience, this occurs when charging from an AC adapter that has the incorrect voltage...or a bad USB cable.
Don't return the phone yet. I had the exact same problem, but it went away after a couple of days. So give it some time to see if it gets better.
If I want to get a longer usb cable(the one in box is ridiculously short), would anyone have any recommendations or any they could link me to? Like cory said I don't want to cheap out on this, I don't think all cables are created equal lol
The samsung charger seems to be the trigger but more importantly, the touch screen is not useable...the phone is fine its just the inputs dont work. Makes me thing the charger isnt regulating voltage and causing a short internally in the touchscreen grid.