My guess: either you have corrupt data in the db or you have the collations (languages basically) for the tables mixed (latin/swedish - utf8/general) which makes joins between tables impossible. If that's the case the "error player skill-data of player with id 1 is missing" could be due to that. Check that the collation for all tables match. If you're using Navicat, right click the tables and choose Table Information and check the DDL. What you're looking for is the CHARSET.
-- Table "list_eventparticipants" DDL
Code:
CREATE TABLE `list_eventparticipants` (
`EventId` int(10) unsigned NOT NULL AUTO_INCREMENT,
`CharId` int(10) unsigned DEFAULT NULL,
`CharName` varchar(128) NOT NULL,
PRIMARY KEY (`EventId`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
Note: my default collation is also "latin1_swedish_ci" and seems to work fine 
HTH
.cha0s