Sony have released some free image and data recovery software for Memory Sticks. If you’ve lost data from a non-Sony memory card, then there are free image recover tools available for all memory cards.
“This online tool requires customers to register the Memory Stick model name and serial number before download of the recovery software can begin. The easy to use Memory Stick File Rescue software can recover .jpg (DCF format), MPEG1 and .mp4 (MS Video File Format) files and in addition, is also capable of restoring most office data files including Powerpoint and Word documents.” (via PhotographyBLOG)
Update: I downloaded this program last night, and used it to recover 102 photos from a Sony Memory Stick that had previously refused to work on my computer or in a Sony Digital Camera, so it’s well worth trying if you have lost photos or have a problem Sony Memory Stick.