It seems to be Reactor Unit 3 which now is having the most trouble as identified above:

TOKYO – A suspected breach in the core at one reactor at a stricken Fukushima nuclear plant could mean more serious radioactive contamination, Japanese officials revealed Friday — a situation the prime minister called "very grave and serious."

A somber Prime Minister Naoto Kan sounded a pessimistic note at a briefing hours after nuclear safety officials said they suspected a breach at the Fukushima Dai-ichi plant that would be a major setback in the urgent mission to stop the facility from leaking radiation.
"The situation today at the Fukushima Dai-ichi power plant is still very grave and serious. We must remain vigilant," Kan said. "We are not in a position where we can be optimistic. We must treat every development with the utmost care."

Evidently I left out a crucial "not" in my last posting:

"There should NOT be such spikes of temperature if this reactor is really back under control."

This sucks big time!

The other reason for shifting from salt water to fresh water is that the salt deposits around the reactor fuel rods interfere with the cooling process from circulating water. Fresh water was not an option evidently when the emergency back-up pumps failed.

Charley Noble