2.1.1 visual editor Insert link problem with Firefox

When I use the insert link button on the visual editor while using Firefox (2.0.0.1), the “Cancel” and “Insert” buttons do not appear on the bottom of the box and even clicking the “x” in the upper right hand corner will not close the box. The only thing I can do is move the box around and am ultimately forced to totally exit the page to make it disappear.

This problem does not occur using Internet Explorer 7.0 and did not occur with Firefox until I upgraded from WP 2.0.7 to 2.1.1. FWIW, I have done a ctrl-F5 (clear browser cache) while on the page prior to using the insert link button.