HELP! Electrical Fault.

We have a 2007 Holiday Rambler Ambassador motorhome that we always winterize and house inside a building. We just got it out and were getting ready to go on a trip this Sunday. We hooked it up to shore power (the same as every year),and were checking the systems when we got an Internal Error message on our panel. The inverter light won't come on, and seems to be 'dead', and approx half of the interior lights work. Nothing on appliances. Prior to this message, I had cleaned the batteries, (unhooked them first) then when I finished, hooked them back up and a few hours later, noticed that the power was off. We flipped the breakers, checked everything we could think of, but nothing worked. We unplugged before going to bed, and the next morning, all was on and working. Well that didn't last long. As soon as I plugged into shore power , got the same message again, and same power problems. I'm wishing it is something stupid that I did, and an easy fix. But...................Any ideas? Thanks

Thanks for all the help. We called Magnum (Inverters) and they said that probably a relay had stuck. Sure enough, we had to unplug shore power, turn battery disconnect off, wait 15 minutes and turn batteries back on, and make sure the inverter is turned on, wait another 15 minutes, then plug into shore power, and IT WORKED! Now we hope it keeps on working.