I cast minor globe of invulerability on my sorcerer, and then cast some skull traps, the globe is supposed to block 3rd or lower level spells, but I'm taking damage from the skull trap, why?

It blocks spells casted directly at you, it does not block spells from conventional traps, spells with area effect, and spells with blast radius like Skull Trap.

------------------
No-Name Face

Dab Nabbit!!!!!! Time to start over

AFAIK, thats a bug. There may be a fix for that on baldurdash.