With only the information you gave--
The printer may be causing a momentary drop in A/C input power to the
computer, due to a turn on transient. This can be caused by using the same
a/c branch circuit,or the same power strip, or even the same plug or
extension cord.
The USB port may not be able to provide enough power, due to other USB
devices.
The USB driver(s) may need updating. The support chipset drivers may need
updating.
The IRQ tables may have something sharing the IRQ used by the USB subsystem.
The USB ports and or the Printer drivers may not be installed correctly.
There may be a conflict between USB device drivers.
More information concerning your system might help to reduce the
possibilities.
When a USB event occurs that causes the system to reboot, I generally remove
the USB subsystem drivers and devices, and reinstall them. When you install
such things as USB printer, camera, and scanner drivers, follow the
instructions carefully.