This is a bug in MySQL that was introduced with version 5.1.24. (see elsewhere on the forum) So you can either downgrade to MySQL 5.0 (beware that version 6.0 suffers the same problem) or have some patience and wait until the release of Umbraco 4 on Friday... it will contain a fix!
So you can either downgrade to MySQL 5.0 (beware that version 6.0 suffers the same problem) or have some patience and wait until the release of Umbraco 4 on Friday... it will contain a fix!