Air conditioner drips at every meal.

I have a 3 yr old Duo-Therm Penquin airconditioner on my 92 30 ft Excella that leaks water inside trough the filter after the air is on for about 15 min. Worked fine all summer then all of a sudden started leaking. Right where I sit when eating of course. Does anyone know what might cause this. I'm in Montana and no Airstream dealers here.