You're getting some tendonitis. I've had it myself, and strangely enough it was from the EZ curl bar on the preacher bench. After I let it heal, I started doing barbell curls with the Olympic bar and kept my form very strict--elbows to the side. Keeping strict form is the only thing that has kept it from coming back. You may come down in the weight you can do, but it is far more beneficial in results and in not getting tendonitis.