From what I'm hearing on NFL Radio....they were in a meeting discussing who to bring in for some co-ordinator job. Marty wanted to bring in his son, the GM didn't, and they ended the meeting. Hours later they called Marty and informed him that they were making a change and he was out. Sounds kinda childish for both sides to me.
That is pretty much the story everyone is reporting, except he wanted to hire his brother. His son is reguarded as a good coordinator with the Jets. http://sportsillustrated.cnn.com/2007/writers/peter_king/02/13/marty/index.html