Depends on if the water is coming from the outside, or the inside. There are 2 "weep" holes (1 on each jug), that are specifically there to drain out water that get by the plug covers. May want to check and see that those 2 holes are open and draining as they should. If plugged, they certainly will hold water and give you the symptoms you have described.
If, however, the water is coming from the inside? Could be time for a head gasket.