If yours is like my 5500 then starter relay is under control board facing you when you open compartment door.. if you saw a flash of light.. I would disconnect all batteries.. solar.. shore .. and chassis power.. you could have a short in control box.. where starter solenoid is.. could be wire connections or critters.. I think there is a fuse mounted on vary front.. maybe that was flash.. use all safety precautions when dealing with rv power.. make a list and disconnect them all.. because you don't want to short something else out and cause even more problems.
Good luck and keep us posted
2000 southwind storm, workhorse custom chassis with 7.4l vortec