M.L.
Ours did too... it could have a mildew problem in the rings. I ended up using CLR, in there. You run an empty cycle with the CLR, then do a simple rinse cycle after that. it should help. if it doesn't then there is probably mildew inside the tubing. You may need to clean the filter, or the drain line
these are some links I found on the subject on what you can do and target the problem:
http://www.howtocleaneasy.com/howtocleanadishwasher.html
http://dbs.extension.iastate.edu/answers/longform.cfm?PID...