Because of the known problem of no scrolling menus in Arduino 1.0.5, I installed 1.5.7 BETA. This removed 1.0.5 of course.
1.5.7 BETA solved the problem and returned the scrolling dropdown menus, but now I find that all other boards I have installed (Pro Mini, Pro Micro and Attiny) have disappeared.
To get the boards back again, I have had to return to installing 1.0.5 with the cut-off menus.
Oh dear!
Martin