I had this happen over a period of 6 months, eating 7 X45s (Best Buy paid for 6...eh heh) at even periods. After I built this computer, it all went away. My suspect was the PSU I had transfered from computer to computer for a couple years; check that. If you have a known good PSU lying around, throw it in and see.
I noticed that powered USB hubs wouldn't work with an X45. Or rather, the other way around.