tabControl and textBox Keypress event:  textBox will not take input.

I'm working on a program that takes several inputs, does some calculations and then plots a graph.  The inputs are handled with a KeyPress event.  All of the textBoxes are in a groupBox control.  Everything was working fine until I decided to put the optional inputs on a separate tabControl with two tabPages.  In the process I did some cutting and pasting of the groupBox with the original textBoxes.  Cut some of the textBoxes out of the original groupBox and pasted them in a new groupBox on the new tabControl.  I also
created a new textBox and places it on the tabControl.

Now the original textBoxes will not accept any input and only beep when I press Return.  The only textBox that accepts input now is the new textBox on the tabControl that was created new (not cut and pasted).
I created a small program with a tabControl and  two textBoxes, one on the tabControl.  It worked fine, so I suspect that the cutting and pasting I did may have tangled something up.  I have tried debugging by stepping into the code, but it never gets to the Keypress event, I just get a beep.

Here's how the KeyPress events are handled:

        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            char c = e.KeyChar;
            int i = (int)c;
            if (i == 13) // The "Return/Enter" key was pressed
            {
                e.Handled = true;
                if (textBox1.Text != "")
                {
                    inputOD = System.Convert.ToDouble(textBox1.Text);
                    Calculate();
                    this.ActiveControl = textBox2;
                }
                else
                    MessageBox.Show("Nothing was entered!", "Entry Error");
            }
        }