Geschosskopf has reported some problems in debugging configs with vague error messages: http://forum.kerbalspaceprogram.com/index.php?/topic/72785-11x-custom-asteroids-131-may-7/&do=findComment&comment=2688063

In the absence of specific criteria to reproduce, I should carefully review all exception messages to find ones that haven't been updated...

Error messages should also name the asteroid group (see later bug report by strideknight).