Comment 3 for bug 301593

@Alexander Sack:

When you set an encryption level other than the default, it would unset "require-mppe" and add "require-mppe-128" (or "require-mppe-40"). If you close the dialog and reopened it, it wouldn't recognize the require-mppe-128/40, and the widget for the require mppe checkbox would be unchecked. If you closed it again, it would save the unchecked state and wipe out all mppe settings. The simplest solution that I saw was to make it write both "require-mppe" and the specific encryption setting.