It is quite probable that Saddam Hussein and Osama Bin Laden were working together.
They had a common enemy: The United States
That had a common cause: The American attack against Iraq in 1991 and the ongoing sanctions
Osama announced in one of his tapes that the US had been responsible for the deaths of over a million Iraqis because of the sanctions, and that this justified his actions.
When the US announced its intent to invade Iraq in 2003, Osama put out a tape theatening retaliation if it did so.
Sounds to me like there was indeed cooperation.