I've had to deal with the same thing off and on.  The pain I have (it's on at the moment) is on the top of the forearms in the meaty part of the muscle (Digitorum and Carpi Radialus for the anatomically inclined).  Basically, over a long time of lifting and climbing I developed a muscle imbalance where my wrist extensors were considerably weaker than my wrist flexors, so that whenever I dynamically loaded the extensors (cleaning a barbell, jumping up to catch a branch or wall top...), I would get mild tendonitis and or muscle strain in the extensors.

The program laid out to me in physical therapy was as follows:

Stretching (do many times per day):

Palm up - bend your wrist back until you feel a deep stretch in the flexors (not the wrist joint) hold for 30 seconds
Palm down - bend you wrist forward until you feel a deep stretch in the extensors (again not the wrist joint) and hold for 30 seconds. If you can already take wrist joint to it's limit (90ish degrees) rotate the arm so that you're putting your self into a sort of arm-bar while holding the wrist stretch.

Excercise:

Don't neglect your extensors!  Although your flexors are what give you your grip stregth, the extensors need to balance the grip by stabilizing the wrist.  Do reverse wrist curls (or better yet plate curls - hold plates in your hand, fingers straight and reverse curl - nice for finger stregth in a std curl too).  Also do hammer manipulations (get a light sledgehammer and rotate the hammer with a neutral wrist and rotate in a hammering motion just using your wrist)

Go easy on the excersice until the pain is gone...

If your pain is in a different place in the muscle, this should be adaptable, but if the pain is right at the elbow joint, go see a PT soon.