help with getting stored procedure's return value in ASP.NET

I have a stored proc that does a
SELECT SCOPE_IDENTITY() after inserting a record. I have tested the stored proc in query analyzer and it returns the new Key Value for the newly inserted row as expected.

In my DAL, I have a TableAdapter where one of the query is as follows (code is generated by VS2005)

        [System.Diagnostics.DebuggerNonUserCodeAttribute()]
        [System.ComponentModel.Design.HelpKeywordAttribute("vs.data.TableAdapter")]
        public virtual object CreateUser(string Afis, string UserName, string FirstName, string LastName, string Email, string PhoneNumber, string RoomNumber, System.Nullable<short> DepartmentId, System.Nullable<short> LocationId) {
            System.Data.SqlClient.SqlCommand command = this.CommandCollection[1];
            if ((Afis == null)) {
                command.Parameters[1].Value = System.DBNull.Value;
            }
            else {
                command.Parameters[1].Value = ((string)(Afis));
            }
            if ((UserName == null)) {
                command.Parameters[2].Value = System.DBNull.Value;
            }
            else {
                command.Parameters[2].Value = ((string)(UserName));
            }
            if ((FirstName == null)) {
                command.Parameters[3].Value = System.DBNull.Value;
            }
            else {
                command.Parameters[3].Value = ((string)(FirstName));
            }
            if ((LastName == null)) {
                command.Parameters[4].Value = System.DBNull.Value;
            }
            else {
                command.Parameters[4].Value = ((string)(LastName));
            }
            if ((Email == null)) {
                command.Parameters[5].Value = System.DBNull.Value;
            }
            else {
                command.Parameters[5].Value = ((string)(Email));
            }
            if ((PhoneNumber == null)) {
                command.Parameters[6].Value = System.DBNull.Value;
            }
            else {
                command.Parameters[6].Value = ((string)(PhoneNumber));
            }
            if ((RoomNumber == null)) {
                command.Parameters[7].Value = System.DBNull.Value;
            }
            else {
                command.Parameters[7].Value = ((string)(RoomNumber));
            }
            if ((DepartmentId.HasValue == true)) {
                command.Parameters[8].Value = ((short)(DepartmentId.Value));
            }
            else {
                command.Parameters[8].Value = System.DBNull.Value;
            }
            if ((LocationId.HasValue == true)) {
                command.Parameters[9].Value = ((short)(LocationId.Value));
            }
            else {
                command.Parameters[9].Value = System.DBNull.Value;
            }
            System.Data.ConnectionState previousConnectionState = command.Connection.State;
            if (((command.Connection.State & System.Data.ConnectionState.Open)
                        != System.Data.ConnectionState.Open)) {
                command.Connection.Open();
            }
            object returnValue;
            try {
                returnValue = command.ExecuteScalar();
            }
            finally {
                if ((previousConnectionState == System.Data.ConnectionState.Closed)) {
                    command.Connection.Close();
                }
            }
            if (((returnValue == null)
                        || (returnValue.GetType() == typeof(System.DBNull)))) {
                return null;
            }
            else {
                return ((object)(returnValue));
            }
        }

In my BLL, I have the following:

    public static short CreateUser(UserProfile u)
    {
        short userId = 0;
        try
        {
            userId = (short)usersAdapter.CreateUser(u.Afis, u.UserName, u.FirstName, u.LastName, u.Email, u.Phone, u.RoomNumber, u.Department, u.Location);
        }
        catch (Exception e)
        {
            // TODO: add logging here
        }
        return userId;
    }
    }

However, whenever the code reaches
userId = (short)usersAdapter.CreateUser(u.Afis, u.UserName, u.FirstName, u.LastName, u.Email, u.Phone, u.RoomNumber, u.Department, u.Location);

I get the following exception.

System.InvalidCastException was caught
  Message="Specified cast is not valid."
  Source="App_Code.-hk-pw4-"
  StackTrace:
       at UserProfileBLL.CreateUser(UserProfile u) in c:\Users\radhikar\Documents\Visual Studio 2005\Projects\IUAAOnline\App_Code\UserProfile\UserProfileBLL.cs:line 94

I have the query's ExecuteMode set to "Scalar" in the TableAdapter.

What am I doing wrong here? I have spent way too much time trying to figure this out.

Please help.