Something is going on inside or outside Reactor 2 Pressure Vessel. Either more thermocouples could be failing, or those that were deemed failed weren't failing.
Here's the latest temperature reading of the Reactor 2 RPV bottom from TEPCO (2/24/2012):
Gradual temperature divergence between 69H2 (now the "official" temperature gauge of the RPV bottom after 69H1 at 0-degree supposedly "failed") and 69H3 (first 2 columns after the date and time column). Up till February 22, the temperature difference between these two thermocouples was 1 degrees Celsius. The difference started to widen on February 22, widened further on February 23, shrinking a little on February 24.
Overall rising trend of temperatures at all thermocouples at "the bottom head" and "support skirt junction". At 6PM on February 18, all temperatures measured at this location was below 30 degrees Celsius; at 5PM on February 24, temperatures are in the upper 30s to mid 40s.
No insight from the media there as to why this may be happening. I'll watch TEPCO's press conference archive later to see what TEPCO had said while I wasn't blogging.