Abysmal Hardware RAID performance - 3ware 9650se

Hi all, I just recently purchased a 3ware 9650 SE 4 lane to setup a RAID array for my video editing workstation. I have 4 Samsung Spintpoint 1TB F3 drives, going into a RAID0 Array (Editing a indie film, lots of HD footage)

I only am using 2 of the drives just to test the setup.

The RAID's sole purpose is to serve up the footage. Rendering, Project Files, OS and scratch disks are all on separate drives.

I am using a 256k stripe, write cache is enabled, StorSave is set to Performance.
Using HDTune, I am getting around 280mbps, a good benchmark. But real world performance is abysmal.

Comparing to a single F3 drive, part one of the movie takes about 3 minutes to open in premiere. Once I move the footage to the 3Ware RAID 0 and open the project it takes around 15-20 minutes!! Unacceptable! On the 3Ware scrubbing through footage is so slow it is basically unusuable.

I even tried using a RAID0 using the same drives and the Intel software RAID included with my Asus Mobo, and It opens in about 2 minutes. Scrubbing through the timeline is very fast. So something is definately wrong with the RAID on the 3Ware.

I'm running Windows XP x64bit. The 3ware card has all the latest drivers & Firmware. I tried all stripe sizes to no noticeable difference.

Any ideas or experiences with this? I want to troubleshoot it, but if not I just have to send it back and try an Areca for a little more $$$. I am going to move to a Raid 0+1 when this is over with....if I can get a working hardware solution....

Thank you all so much, I'm about to pull my hair out...