Sorry some of the previous answer I gave was not correct. You did not give model of machine in your first question so I assumed it was a dish drawer. The rubber ring sounds like it may be the o-ring for the wash pump. The main wash pump fits up into the plastic sump. There should be an o-ring fitted in here. May also be the cause of the leak which has appeared. Lay the washer down on its side, remove bottom tray and then disconnect & remove wash pump from sump. Fit new o -ring and re assemble.
Lincoln Appliance NZ, December 2008