Yes... A long time sporadic troll finally coming out of the dark here... But since the forums aren't as busy as they once were I thought I actually contribute a bit.

By MBR do you mean your partition table? If only your partition table is hosed you could pretty easily reconstruct it using something like a live boot cd (knoppix, system rescue cd, gparted come to mind).

If you're lucky most hard disks start their first partition at sector 63. So running fdisk (the one for linux allows you to use the -u option to change units to sectors, I haven't touched Microsoft's fdisk for years so not sure what the flag would be for that one) create you partition starting at sector 63 then setting the ending size to the end of your disk might allow you to once again mount your filesystem.

There are more complicated ways using TSK (the SleuthKit), to find your filesystem's signature to know which sector offset it starts at then reconstruct the partition table from that information but trying the sector 63 trick might be the quickest and easiest.

Another tool I've used that can look for filesystems on a block device (regardless of the state of a partition table) is called testdisk, so something else to try if you're still having problems.

Good luck.