Hmmm... it shouldn't be any problem. It has fairly fine thread (a lot of engagement) but Jim is right about a frame wrench. I've done it with a block of wood but never had any problem. Yours, apparently, has something else going on.
Could you have damaged the barrel threads when you drove out the pin? You know, moved a little metal so that it is more difficult that usual to remove it.
By the way... I use a real barrel vise. What are you using?