My world has been reverted!! HELP!

[Scoobymenace]

Hi i would like to start off by saying that when i had recently updated tekkit to minecraft V1.2.5 i started to update my world, although as soon as i had got on to the world everything had been reverted all the way back to when i first started building there and i cant find any back ups or how to put it back to how it was ! Thats about 50 hours of gameplay gone down the drain because of the bloody update, but another thing to mention is that my other world that isnt as far hadnt changed a bit and was still like it was before the update, im confused and very sad that all of my stuff has gone. any solutions on how to fix this would be great thanks.

[AlienX]

I assume you followed the normal instructions for updating your world to 1.2.5 from 1.1?

Also, if you did not make any backups, then unfortunately that's your own bad. (and yes, i know how annoying it is!)