Epson Printer Stops printing when I unplug any usb device...

If I unplug any usb device from my computer while printing from Photoshop on my Epson 9600 it stops in the middle of my print and gives me a communication error and then just cuts my print right off. This happens when I plug in or unplug my Iphone, any usb drive, or any of my external hard drives. What could be causing this and does anyone know how to fix this problem?