EVGA 730i SATA bus super slow

I have the following components:

EVGA 730i motherboard
Q9550 CPU stock clocks (OC after issue resolved)
2x 2gb Corsair XMS2 ram
1 blu ray SATA drive
2 DVD SATA drives
5 SATA hard drives
EVGA 8800GTX ACS3 video card
Corsair 450 watt psu
Windows XP Media Center 2005

You would think this is plenty of system to play a dvd and copy dvd data at the same time. I know it should be but as long as Im not doing anything else the movie plays fine. As soon as I try to copy data that uses the SATA ports the movie lags horribly bad and is unwatchable.

I contacted EVGA about this and tried different memory and removed a usb wireless adapter and the software that is sometimes known to cause this issue. No fix was found. They did issue an RMA and I intend to do it but I wanted to ask the community here if anyone else ever had this issue before.

My motherboard also had an engineering BIOS installed that said it was an engineering sample not for resale. The issues I was having forced me to update the BIOS to the latest version which fixed nothing. Obviously I just got a bad motherboard that was used for testing purposes.

Thanks for any input you have...

I ended up RMA'ing this board. I messed around with for days with no change in performance, not that anyone seems to be interested in this thread..