I too have had this kind of pain. Not just in my fore arms when I curl but also in my collarbone area when I bench. I understand what you mean by saying that it feels like stress on the bone is causing it. And yes strangely enough once I put the curl bar down it hurts but not for 20 seconds it just hurts for a couple of seconds.

I can't say that I did anything specific to make it go away I just switched exercises. Eventually the pain abated and I went back to the old exercises.

I had this exact same thing from doing ezy bar curls. Originally I thought I'd fractured it or something as at the time I had a bad habit of trying to block round kicks wax on wax off style, but a friend of mine suggested it might be tendonitis, and he was right. I switched to hammer curls which caused me little to no pain at all, and now my arms feel fine.

(valgus being the natural posisition of the forearms, they lay off at an angle to body, notice when you turn your palms up and have your arms down by your sides they dont make a straight line, straight bar forces them into an unnatural posistion)

If you get pain in the elbow it could be medial or lateral epicondylitis, RICE principle dealing with that. And up your Omega oils intake, like 8-12 grams a day.Fights inflammation and Usually makes the pain disappear hastily.

As for forearm pain it could be Pronator syndrome which is the entrapment of the median nerve or it could be Radial nerve injury. When curling the hand is pronated causing the nerve the become trapped when the forearm muscles are contracting. Dealing with the problem is harder, because the pain tends to occur when gripping with the hand turned palm up, i recommend to my athletes to try neutral grip bars or hammer curls instead (of straight bar), Band curls help also.