i have been able to remain friends with a few of my ex-girlfriends, but it is really hard. in any breakup their will always be one person who has to do most of the forgiving. in the most recent case that has been me. you have to sholder things, forgive them without raising the issue etc etc...
my last girlfriend and i had great comunication with eachother, and this has carried through into the friendship stage. even still, there are really rough days.
i really like her new man, and have been giving her some relationship advice to help things along. i had to push hard to meet him, as they were both worried, but the gentle persistance paid off.
he has come to a couple of club nights where i have played, and we all go out for beers every now and then
it has taken nine months for us to get to this stage though, and again, i have done most of the forgive and forget stuff. when it is worth it, i think your more willing to suck up some of the hurt they throw at you.
now i just call her on her shit when she tries to dump it on me, not by throwing it back, but by refusung to acknowledge it. give her a little look and she knows she is being an ass, and vice versa.
from the begining of the break up though i knew i was willing to work hard at being her friend. it helps that it does not hurt to see her with others, but that came with lots of time.
we were together for years, and i guess that helps to a large degree in terms of even wanting to remain amicable with each other. good break up helps too. no one wants to remain friends after a messy ending.