Here's a solution that worked for me, however you do need to use the service mode (which can be tricky for the first few times):
http://forums.minidisc.org/viewtopic.php?t...r=asc&start=179
"Just found that it may be useful. In case your MD disc has its TOC messed up, or the disc can't be "All erased", try this: Go to service menu 518 (erase), set the value to 00 then press "pause", allow the machine to run up to after address 032. The TOC of the disc is now cleaned and become a fresh blank disc."