Reply...
Rmalone,
It's likely an error caused by the fact that you have more than 100 aircraft (including multiple skins / repaints of one aircraft) in your aircraft folder. In that situation it causes a failure of quick combat, mission builder, and the "info" screen in missions.
To fix, you'll need to reduce your plane limit to below 100 first, either by creating another install, eliminating some aircraft, or using Martin Wright's AcMan to create a separate hangar for the extra planes.