Null reference exception when trying to use DataAdapter Update

Question

I keep getting an exception when I call the DataAdapter Update method. I have been trying to figure out what is causing the null reference exception for this code for what seems like forever. The exception information has not been helpful. All it says is: "Object reference not set to an instance of an object." Does any one have any idea what is going on here or how to go about finding out? Any suggestions would be appreciated: I don't even know how to figure out which reference is null!