I know there have been lots of threads concerning this phantom menace, it has bothered me recently as well. Just wanted to let some people know that i have found out what relieves me of the problem, in case anyone else still cant figure it out.
After being frustrated and in pain for months, especially during direct bicep work, i decided to slow down and evaluate my form...drop the weight a tad. I noticed that while my overall form was good, the one thing i was overlooking was my wrist position. At the top of my bicep curl i was curling my wrist inwards as well. Over time (and volume), i belive i had developed an imbalance in strength between the muscles on the underside of my forearm and the top of my forearm. I started doing my curls and really paying attention to keeping my wrist straight during the entire ROM and the pain is slowly getting better. My last arm day i was back up to doing my sets at 105lb with no problems at all.
So if youre still having trouble with this, inspect the position of your wrists during your curl movement. Ez-bar, straight bar....can do em all now np.