First question, usually able to sort things out without needing to make a post:
I left a craft in [what I thought was] a stable 300km circular orbit around the Mun last night, with Mechjeb holding the craft prograde. I wake up this morning to notifications that it crashed into the surface! I had all engines shutdown, so there's no chance it was caused by errant throttle, and Mun has no atmosphere (even if it did, I would have parked well above it); so what caused my craft to lose orbit? I've left crafts in Kerbin orbit overnight, and not lost them, so is this just a bug with the Mun, or a general bug that needs fixing?
Jeb's dead, baby.
Edit: if it makes a difference, the craft in question was a 2.5m fuel depot (fuel tank, solar panels, batteries, monopropellant—all the necessities to resupply in orbit) with a smaller SSTO docked to one side, so the controlling module was not directly in line with the cG, though it was parallel on all axis; see attachment for pic (sorry it's dark, Kerbin was eclipsing the sun, and we were about to head behind the Mun)
Mods running (though I don't see how they'd cause this) include:
Mechjeb, KW redux, B9, FAR, KSPI, RPM, KJR, Chatterer, Hangar Extender, and RCS Aid.