If it got to 62 today, that would have thawed anything in the gray tank and/or pipes. You say you know there is water in there, the first thing I would do is remove the drain hose, and open the gray valve (that is the auxillary) The turn on the tap in the bathroom and the kitchen, and walk outside to confirm there is nothing running from anywhere. Hopefully, you will see it draining properly from the pipe to the ground. If it isn't, then insure it isn't draining out of the belly pan somewhere. If it is, that would indicate a cracked tank or drain fitting. If it is not draining anywhere with the water running into the drains and the handle pulled on the gray valve, then I suspect you have pulled your handle loose from the valve itself, maybe when it froze the other day? If that is the case, either you or a repairman has a pretty good job ahead of them. It is not an impossible one, however.
2000 390 Landyacht XL
1989 29' Excella
WBCCI #6673 jerry Hodge
Have no intention of arriving at the grave safely, but rather to skid in sideways, chocolate in one hand,throttle in the other, totally worn out and screaming
"WOO HOO, WHAT A RIDE!"