AI've made SMBC several times with NO problems at all. I've just spent the last 2 hours and a whole carton of eggs on this batch. The first 2 times the eggs started to cook before the thermometer hit 100°F. The last few times they started cooking right at 100°F. I'm not doing anything differently than I did before. Is it possible that I just got a bad carton of eggs? I'm so confused!

AWas your pot directly touching the water? Was it boiling? I think it should only be simmering water, the bowl not touching it directly.. I use carton eggwhites too.

ANope, not touching water or boiling. Very light simmer and quite a few inches between the bowl and pot of water.

ANope, water was about 6 inches from it and on a very low simmer.

Did you have one of those thermometers that are a glass tube sitting in a metal holder, with the temps printed on the metal strip.  The glass tubes do slip up and down in those metal frames sometimes.

Test your thermometer by checking the temps of boiling water. here's a helpful thread.

http://www.virtualweberbullet.com/thermotest.html

AYou should be able to dip your fingers in there and feel around 110 degreesF. It should feel like warm bath water. You still need the thermometer, but your fingertips can tell if the thermometer is that far off.

AI actually have 2. One is a large metal thermometer and the other is the one you mentioned. I tested both and they had the same reading. This is just so strange.