Follow-Up:
If your Rialta is still under warranty (it is for miles, but maybe not for years depending on when you bought it), I'd have to agree with Dan. Call up VW and tell them that the unit is still under warranty and you need it fixed. You may want to do the same for Winnebago -- they've always been very nice to me when I've called them, even for VW, Onan, etc. problems. You'll probably have to be firm, but keep it fairly nice or you'll get nowhere.
Here is a link that might be useful: www.MotorHomepage.com