thats not entirely correct, Belthan. they do'nt CHANGE your birthsign, they just give you a nice power(up to 4 or 5 max), but i know where the glitch came from now:
molag bal quest:
after you die your magical effects dissappear sometimes, sometimes if you play 3rd person you lose your body(its invisible!!) and 'my glitch' cant be corrected unless i load a previous save

which i dont have... convenient!
so SAVE before the molag bal quest!!!