Currently I have no knowledge of any MySql clients that fully support v4.1 apart from mysqladmin. Ritesh promised a new version of SQLyog compatible with 4.1 to be released later this month, and MySql AB has been developing a new ODBC driver (v3.52, currently in alpha) which will comply with the new binary protocol of MySql 4.1. There is only one workaround to this problem: do not use passwords, users without password are able to connect to the server. If security is too important, then I suggest downgrading to 4.0.x.