I get that error upon trying to insert/update.041226 22:45:48 read_prev_with_key: Got error 127 when reading table: ./path/to/table
I ran myisamchk.exe with -r, -f, -o, etc.... they all just checked the database for about 10 minutes then said it's fine.
When trying to browse the database via phpmyadmin it just does not respond and my cpu usage goes all the way up to 100% and I have to kill apache and mysql. My php scripts can however browse through the database.