I am at the moment updating drivers /bios for my raid card and came across this in the Promise faq
If one of the RAID 0 hard drives has failed, it is not possible to recover your data. If all of the members of the array are still functioning, it may be possible to recover your data. In the FastBuild BIOS utility, delete the array and re-create it [ IMPORTANT: Make sure that when you recreate the array you use exactly the same array settings (RAID level, drive assignments, and stripe size) of the original array ]. Going offline may indicate trouble with a hard drive, so it is recommended to perform a data backup and then perform a disk diagnostic on the hard drives.
This is using an add on raid card you dont say what you are using