Agents - Much like real life, a player plays one good game, then the agent tries to get him a new contract, even though the player has been at the club for 2 months, you refuse, the player wants to go!
Issue a hands off warning - TWICE this thing has f*cked up a player for me, I issued a hand off warning over one of my best players, next thing I know I'm getting a barrage of abuse for saying I'll let the player go(???), the player says he wants to stay, then hands in a transfer request? I know for a fact I issued a hands off warning, yet this happened to me
Other teams scouting - One team in particular was scouting no less than 17 of my first team player, then made silly low offers for important first team players, this caused a lot of my players want to leave, or feel pressured by the interest shown in them, causing problems in my team
Promote a player from the reserves - Morten Rassmussen (sp?) comes back off a season long loan, during this loan I place the player in the reserves so he doesn't clog up my first team player list, on his return I promote him to the first team, he complains about being placed in the reserves, requests a transfer, which I accept, he then goes public saying I'm forcing him out the club and he wants to stay!?
NB: My team is Celtic, on my first and only season I won the treble, not boasting, just so you know I don't have a sh*t team at the bottom of the league 8-|