I have the Sony MZ-R700 and for some reason it will record 20 minutes and then do the TOC and then be done. If I hit record again it will record 20 minutes do the TOC edit and done. Any idea what happened?? I checked the manual and nothing.
You could probably get better answers here:
http://forums.minidisc.org/index.php?showforum=34
But from your description, it sounds like your MD is gone.
Did you try different brands of blanks?
If you have warranty, send it back for repair. Otherwise it's probably not worth it. HiMD recorders can be picked up on ebay for $70-80 these days...