A Predicted Failure is when the bad blocks on a drive exceed a predetermined threshold. With a Predicted Failure you can continue running, but are running the risk that if another drive in that array fails, then you may have an issue with those bad blocks being rebuilt across the array. I would suggest replacing the drive, but when doing so there is a procedure to do so. To replace a Predicted Failure drive you need to go to the controller, or OpenManage, and force the pred fail drive offline. Once it is offline then you can remove and replace the drive. If you were to simply remove the predicted failure drive before rebuilding, then there is a chance of carrying the predicted failure to the new replacement drive.
Let me know if this helps.