While upgrading to current CVS, in the process I got:

Incorrect integer value: '' for column 'public_key_expires' at row 1

INSERT INTO mdl_mnet_host (wwwroot,ip_address,public_key,public_key_expires,last_connect_time,last_log_id,deleted,name) VALUES(?,?,?,?,?,?,?,?)
[array ( 'wwwroot' => '', 'ip_address' => '', 'public_key' => '', 'public_key_expires' => '', 'last_connect_time' => '0', 'last_log_id' => '0', 'deleted' => 0, 'name' => 'All Hosts', )]

• line 253 of lib/dml/moodle_database.php: call to debugging()
• line 272 of lib/dml/adodb_moodle_database.php: call to moodle_database->report_error()
• line 178 of lib/dml/mysqli_adodb_moodle_database.php: call to adodb_moodle_database->insert_record_raw()
• line 88 of mnet/environment.php: call to mysqli_adodb_moodle_database->insert_record()
• line 25 of mnet/lib.php: call to mnet_environment->init()
• line 9 of portfolio/type/mahara/lib.php: call to require_once()
• line 628 of lib/portfoliolib.php: call to require_once()
• line 43 of admin/mnet/adminlib.php: call to portfolio_static_function()
• line 191 of admin/mnet/adminlib.php: call to mnet_get_functions()
• line 387 of lib/adminlib.php: call to upgrade_RPC_functions()
• line 76 of admin/index.php: call to upgrade_db()

Ciao