¿Has leído esto?, tomado de
http://dev.mysql.com/doc/refman/5.0/en/news-5-0-54.html
Parece ser un bug y hay un parche que lo corrige.
When doing a DELETE on a table that involved a JOIN with MyISAM or MERGE tables and the JOIN referred to the same table, the operation could fail reporting ERROR 1030 (HY000): Got error 134 from storage engine. This was because scans on the table contents would change because of rows that had already been deleted. (
Bug#28837)