SUCESSFULLY TESTED SOLUTION:
I got stuck with the same problem today. I downloaded "GetDataBack for FAT" from http://www.runtime.org . This is a data recovery software. I was able to sucessfully retrieve my photograps from the currupted Sony's Memory Stick. After retrieving the photographs (phew!) I formated the Memory Stick. Everything is back to normal now.
I am sure this will help and save botheration of going to Sony Service Center and Paying them for faults in their products.
All the best