I have experienced exactly the same problem with the Sony RDR-VX450.
I'm afraid if you load the DVD into a PC you will find that your recordings have been erased. I don't know any way to get them back. Are you using DVD+RW or DVD+R disks? It seems that the finalisation process fails and when you load the disk again the machine fails to recognize the files and erases the disk automatically!
This error seem to occur when using DVD+RW and DVD+R disks, and/or using the recorder in VR mode, which suggests there is a problem with the disk finalisation process which is automatic if you use DVD+ disks.
The advanced features of DVD+ do not appear to be correctly implemented in VR mode on this machine, perhaps indicating an internal software problem.
I would suggest you change to DVD-RW and DVD-R disks only, and change the default disk format mode to Video instead of VR: this seems to resolve the issue. Disk finalisation, when performed manually on DVD-RW disks recorded in Video mode, works normally; such disks are also no longer corrupted or automatically erased.
