Originally Posted by looseintheadset

I registered here to post my solution to my cross bike's seized/stuck/stripped GXP crank arms to help anyone else who finds this post via Google.
This trick should work with any threaded external bearing system, not just GXP. My GXP arm's internal screw was stripped out by it's former owner and I didn't want to buy some sort of automotive puller. So...

1.) Remove all bolts/screws from the GXP non-drive side arm so the only thing holding it on is whatever is seizing it. Apply a penetrating oil if you want.
2.) Carefully wiggle a bottom bracket removal tool around the left crank arm and into position on the BB. (Your crank arm's design may not allow this, however...)
3.) Unscrew the non-drive BB and with it will slide off the crank arm as it unscrews. I had to use some creative leverage to get it started, since the BB was badly stuck, but that is a much simpler matter.
Note: You may need to back off/on the BB and adjust the crank arm to get the best tool position as you work. (Also, be sure you are turning the right direction!)

There you have it! I haven't felt so satisfied with myself in months as the moment the crank arm slid off. Hope this helps someone else searching for a solution.