The problem with mine was my motherboard, I also replaced my USB hubs with 2.0, even though the hubs that i had previously said they were 2.0 "well they were not 2.0". Mind you the PC upgrade was well worth it!

Asus M4A88TD-M-EVO-USB3
AMD 1090t x6 @ 4.2ghz, with 8GB DDR3 1333
Gigabyte HD5770 1GB (overclocked)
1.5TB HDD & 250GB HDD samsung SATA 2
1x 24" LCD 1920x1080, 1x 42" Plasma, 1x 50" Plasma 1920x1080.
TPG ADSL2/2+ 25mb/sec 130GB, 100mb/1GB/per sec, wired/wireless/bluetooth network.