Soxman,
I read somewhere that you may need to replace the cathode (anode?) rod in your hot water heater.
However, other sources indicate the smell could be due to bacteria. This link explains how to clean your system:
http://www.ehow.com/how_7771_clean-rvs-water.html
Here is more about a sulpher smell:
http://groups.google.com/group/rec.o...9eccd868dc4975
See what others have to say before you get into a big cleaning/parts changing project.