Simple. Fireball spells and Ice Spike spells have 0% effect! ZERO! NADA! *rage*
If it is Mzulft, I got stuck there too. You have to use the Flame/Icethrower spells. (The ones that do damage PER SECOND, rather than 1 single blow.)
Perhaps I'm the only one dumb enough to make this mistake, but there you go.