What should I do with this friend of mine?

I speak to a girl who is a close friend of mine and we spoke all the time and loved it but I left for week with no communication – and as soon as I got back, we rarely spoke and when we were both on msn it wasnt the same and kinda boring. It might just be that conversation but if its not – is there any good ways to get it back to how it was or should I just let it ‘rebuild?’ it sounds sort of pathetic if you cant relate to it…