Happened to me when I was about 7. 23 years ago and it still hurts!
My advice:
Don't be afraid to express exactly how you feel.
Find out the facts of what went wrong.
These things will haunt you otherwise. Separation and divorce is never a pleasant thing and its always different in every single case.
I was in a vulnerable position at that time and court appearances and a parent moving out are deeply traumatic even if I did block it out at the time!
http://www.fathers-4-justice.org/f4j/