it's possible for sure, but you gotta give it some time.
my best friend /sometime lover (heh) is well, still my best friend. but that's a special relationship i can't even begin to explain.
i consider my first boyfriend to be an awsome friend now. granted, we didnt really talk for a year. i was living in the same house with him and my then so called 'boyfriend' so there was jealousy and hatred and some weird little circle. just not a good situation.
i was a complete ***** to him and felt really really bad finally. we had severed all ties and i had to go thru a bunch of people to finally find his email address (he had moved and gone to south america and back again) so i got that and told him to call me and we had a long conversation. thank god i tol dhim i was sorry because there was no reason for being enemies. i finally saw him in november. i flew to where he was living to see him and it was great. needless to say we are great friends. we talk every week and all that jazz, and i'm grateful for that.
granted, we didnt date that long but we were able to have that friendship before we started dating (which wich other relationships we have just gone right into boyfriend/girlfriend).
there's one 'ex' i don't talk to and wish was dead.
the ahem, older gentleman i dated and i still talk...but i think there is some weirdness there. it was a very sexual relationship and i think from his point of view, that he would rather be pardon me, f-cking me instead of just hanging out with me. that whole older guy/younger woman thing was a big ego boost for him i know. we are still friends and we actually dated for a significant amount of time, and he's a great guy.
my most current ex..we were really, really serious despite not dating for very long. we were talking marriage and all that jazz and all the sudden broke up. and it sucked. and i was bitter towards him. i finally talked to him about how upset i was about things and whew...we're friends again. and it feels great. because i couldnt look at him without hating him for a while.
so yeah, it's possible..but you two really need to TALK! you have no idea how much it helps. and i mean really talk...i have had 6-7 hour long conversations that sure, get pretty damn repetitive but sometimes you gotta do it.
you can have that platonic friendship. sure it's hard if you were really serious and /or were in love, were sexually involved...and you'll always remember that and probably long for it at times, but just know you guys arent right for eachother and laugh about it. realize friendship is the way to go.