Again, please don't post any errors about SCT until you have tried reseting your options with the Reset button or using /sctrest.
I still don't know what is casuing it, but I have added code to the next version that should stop it from happening. Switching to the whole nil based flag system was a bad idea
In better news, I have a new addon mod to SCT coming out soon called SCT - Damage. Its going to allow you to see the damage you do to your targets, but in a more general/static way than the way the default WoW engine does. Its not going to be perfect, or have near as many options as SCT, but it should allow you to see your damage in a more consistent way. And it won't be effected by mob size and such. I have the guts of it finished now, but am currently working on the option page and how it will all integrate into SCT. Expect it in the next 1-2 weeks.