Horrible choppy/bubbly playback

Hi, 

I'm sure this question has come up loads of times but I can't seem to find an existing thread for it, so I thought I'd ask here.

My playack in Audition is terrible. (Sounds like a radio playing under water). I'm not very smart with Audition but I have used it for over a year. I had to stop my subscription for a couple of months but I restarted it again recently (though I can't this would have made any difference with the playback).

I am editing some music on it and even the sessions that played back fine before, now play back terribly.

It seems to export the track perfectly, but that doesn't help me with editing.

All the files were created on Garaeband and exported individually to MP.3, then imported into Audition. As I say, I have been done this many times before over the last year and it has worked fine.

I have both changed the sample rate in Audio Hardware preferences and I've changed the bit depth and sample rate in the .sesx file (following advise from a youtube video). 

Unfortunatley nothing seems to make any difference. Has anyone got any ideas?

I'd really appreciate anybodies help.

Sorry if you've seen this question in some form a thousand times before. I just really couldn't find it if its there.