Just got back into training after a 2 year break (ugh).

Going on my old program that worked wonders last time but every time I do forearm curls after about the 5th rep I get a pain in both wrists.

I am kneeling next to a bench and resting my arm on top palm facing up.

Any ideas why this is happening? My wrist is giving out before my forearms get a proper workout.

As soon as I stop, the pain goes away and it happens to both wrists.

Whenever I would get this problem it would be because I did not stretch out enough.especially with my wrists and haflway down my forearm.

Your body might not be use to doing them right now.
Are you using a straight bar or curved bar

It's probably just due to starting out of nowhere again. Lower the weight a little, and keep at it. Your wrist ligaments should toughen up after a week or two.

Have you tried using wrist straps? I'm a big fan of them as they help alleviate and disburse tension and provide support for the wrist. I generally tighten the straps when I need extra support, specifically when doing heavy forearm curls, and any type of press exercise.

By wrist straps, I'm talking about the straps that wrap around your wrist and can be "velcroed" into place.

Have you tried using wrist straps? I'm a big fan of them as they help alleviate and disburse tension and provide support for the wrist. I generally tighten the straps when I need extra support, specifically when doing heavy forearm curls, and any type of press exercise.

By wrist straps, I'm talking about the straps that wrap around your wrist and can be "velcroed" into place.

that is a good way to "band aid" the real problem which is you not having enough strength in your forearms..
if you are deadlifting more then your body weight without straps I can almost guarantee you wont have any pain in your wrists