cell click problem using data grid view
 

hi,
I am using a generic list in a class and I connect this list to a binding source which is connected to a data grid view using the DataSource and DataMember properties of the data grid view. when i add the first object to the list a new row is added to the data grid view. when i click the first row I get an exception: "index -1 does not have a value". if I add another row and click the second row in the data grid view I do not receive any exception.
can someone tell why i receive this error?
thank.