5.2TB RAID

The problematic RAID is 5.2TB RAID6 in ext3. I mounted it as large LVM on RedHat EL4 server, and I accidentally issued a GRUB command: setup (hd0) into it (under the instruction of a redhat tech), now I can not see my LVM anymore and Redhat EL4 only recognizes it as a “RAW” disk (/dev/sda, fdisk -l reports no partion). I think the MBR/partition table is overwritten, Can anyone help? Thanks