Sounds like the pipes have become overloaded with old grindings from the disposal and it's backing up. Hopefully that's all it is, and not a clog somewhere further down the line.
Pour 1/2 cup of baking soda in the disposal, then add juice from a whole lemon or two. Wait ten minutes, then pour a pot of boiling water down the drain. Wait 30 minutes then repeat, running the disposal the second time.
If you still have problems after that you will want to call a drain guy. If you're in the San Diego area, let me know...I have a GREAT drain guy and he never over-charges!!
at 7:28 AM on Jan. 12, 2009