Does the Tab key still change the selection? The .Text property is only available if the Textbox currently has focus. If it doesn't have Focus, then you should use the .Value property instead (or just reference the Textbox directly).
The .Text Property only stores data while a textbox is being actively edited. As soon as you change the focus, Whatever's in the .Text property gets saved to the .Value property and the .Text property is cleared.
If it has Focus
Code:
strVariable = Me!txtMyTextBox.Text
If it does NOT have Focus
Code:
strVariable = Me!txtMyTextBox 'Same as using Me!txtMyTextBox.Value