We just stayed at Olema Ranch Campground for three nights and also had a weird electrical problem. We didn't get shocked or anything, but they had just been flooded (again) two weekends ago. When it was time to leave, I turned on the water pump to wash our hands in the TM sink after we disconnected, but nothing would work. I checked the 12V inline fuse, and it looked OK. I also checked the batteries with my digital voltmeter, and it didn't register anything. It seemed as though the batteries were completely drained. I know that they were fully charged when we left, and left in the fuse during our stay. It seemed weird that our 2-year old 6-volt Trojans would just die like that. I cleaned off all the connections, etc, but nothing helped. Both batteries were full of water.
After poking around some yesterday, it turns out that the batteries were charged, but the inline 12v fuse (although the filament was intact) was the problem. There was some brown discoloration inside the glass. What's weird is that my digital voltmeter (as I found after I took it apart) at this very point in time decided to sever the positive wire connection in the center of the plug (it is the plug-in type). The design is such that the contact point at the end flexes in and out and causes wear to the sodered joint, eventually ending in up in a severed connection. I sodered it back, put in a new 12v fuse, and now everything is wonderful. I'm going to buy another voltmeter to take along as a backup.