Ok, this is getting really bad. It is not full on meltdown, but it's damn close.
From the experts who I've talked with:
For Unit 1, at least some of the core remains exposed and there is no word on the status of the spent fuel pond, which could ignite if water levels are not maintained.
When the IAEA released this document, Unit 2 was stable due to a temporary cooling measure. Now, the IAEA reports that Unit 2 “has experienced decreasing coolant levels in the reactor core.” This is the same failure mode that has afflicted Units 1 and 3.
Unit 3 has lost control of its valves, which were used to vent to reactors, leading to a dangerous pressure build-up (and no ability to pump in water).
I think we are now heading to three full core melts. Chances are, if the containment vessels are breached, the cores will melt through the bottom. There is a small possibility of a vent that would spew radiation. Bob Alvarez points to the possibility of a plutonium fire in the spent fuel ponds, which is a total wildcard. (See what the National Academies had to say about this possibility.)
And the IAEA:
http://lewis.armscontrolwonk.com/archive/3648/iaea-on-fukushima
Other updates:
http://lewis.armscontrolwonk.com/archive/3657/another-fepc-statement