Symptoms
The Navigation Pane in Access is too narrow, and you can’t widen it by using the (double arrow) along the right margin of the pane.
Cause
This is an intermittent problem with some versions of Access.
Resolution
Right-click the Navigation Pane title bar and then select Search Bar. The double arrow should now appear on the right margin of the pane. You should now be able to widen the pane again using the double arrow.