Coach 12V power/Generator question

[rpgibbs]

We bought a 2000 Lexington 283GTS several months ago and are stilling getting familiar with the RV. Something happened today that has not happened before and I need some help as to what the problem might be. I have started the generator about 6 times or so with the RV plugged into 120 ac (it is in storage) with no problems. Today I went to work on the RV and this is what happened. I turned on the 12V system (I disconnect the batteries when I am not there with a key switch near the door) and some ceiling lights with no problem. I then tried to start the generator (Onan Microquiet 4000) and it cranked a second or so and stopped and then the interior lights went off and there was no 12V power anywhere in the coach. I then checked all of the fuses (under the rear bed) and they were all ok. I then plugged the RV into 120V ac and the 12V Coach system started working. I then stated the generator with no problems. When I have started the generator in the past the RV was always plugged into 120V power and I never had any problem. Where might this problem be located? At the generator, the inverter or might I have a faulty relay? Thanks