You might have to go talk to Baldur Goldpaws in Wizard City (near the Bazaar) before you talk to Erik. I think I remember having to make a side trip to Olde Towne before getting started on the spell quest.
Nevermind, pardon me. I failed to complete a prerequisite quest, namely One in the Snout.
It is an odd prerequisite, considering it has nothing to do with the spell quest. I believe the quest that unlocks Mirkholm would make more sense as a prerequisite.