Update Stored Proc Not Working

I'm trying to run a UPDATE stored proc to allow my users to update records that are in a datagrid. What the update proc looks like is as follows:





Proc sp_UpdateRecords


@fname nvarchar(30), @lname nvarchar(30), @address1 nvarchar(50), @address2 nvarchar(50), @CITY nvarchar(33), @ST nvarchar(10), @ZIP_OUT nvarchar(5), @ZIP4_OUT nvarchar(4), @home_phone nvarchar(22), @autonumber int


AS


UPDATE NCOA20040603 SET fname=@fname, lname=@lname, address1=@address1, address2=@address2, CITY=@CITY, ST=@ST, ZIP_OUT=@ZIP_OUT, ZIP4_OUT=@ZIP4_OUT, home_phone=@home_phone


WHERE autonumber=@autonumber





The message I'm getting is as follows:





Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index








What could be the problem





Any ideas are appriciated -- Thanks in advance


RB