Disk not accessible any more (My Book Studio Edition)

I was using My Book Studio Edition 2TB formatted in NTFS, and in RAID 1. I was using it from Windows 7 (on an iMac through FireWire). 

Few days ago, the partition just disappeared - no data is visible any more. Windows says that drive needs to be formatted to be accessible.

When I try to run WD diagnostics tool - it reports drive as healthy but unformatted (???) and recommend that I format these drives.

I tried to run some of the freeware data recovery tools on it - it took 24hrs to scan - but failed to find any useful data (I had tons of ISOs & JPGS on it)

Any recommendations on how to recover the data on the drive and should I return the drive as faulty? (and how to prove that something happened?)

Thanks,

/Tomislav

Here is a report from WD diagnostics tool:

Test Option: QUICK TEST
Model Number: WD My Book (RAID 1)
Unit Serial Number: WU2Q10155871
Firmware Number: 1015
Capacity: 1000.20 GB
SMART Status: PASS
Test Result: PASS
Test Time: 14:32:24, September 20, 2010

It doesn’t sound to promising. I’ve had some similar problems with a MY Book Pro in Raid 0. I’ve done 2 things to recover one is to remove drive properly thru USB then reboot and plug drive back in. The other is to delete the driver shut down disconnect drive boot and plug drive back in. I found a third party defrag program was causing my problem.

Joe