USE THE EZ curl bar!!!!! thats why your forearms hurt trust me. I've really messed my self up doing curls with a normal barbell, where I couldn't do curls for a year, the EZ curl bar is designed to give less stress to your forearms. Luckily I guess my forearms have built up strength over time and now the straight bar doesn't hurt quite as much. Now I do what Gixxer said and release my hands very slowly after I put the weight down. Seriously though don't use a straight bar anymore, you'll thank me later.