Could be the PSU. I had a similar problem when I added an extra dvd writer. I upgraded from a 300 watt to 500 watt.
The ATI Radeon X""" series. must be connected to a power source. Usually the hard drive. My SATA hdd didn't like this so connected it up to the lesser used writer. I have the x1300 tho. Only 256memory on board
Seems ok now
Hope it helps.