Flash between computers

Ok, I’m getting some really weird problems, and I have no idea wtf to do… I made a small game, and it updates high scores to a database via ExternalInterface calls, and displays them on the page. It was working perfectly fine one day on mine and all my friends computers. Then today, none of the ExternalInterface calls were firing (wtf?). So I checked on my gf and her sister’s computer and they work fine, but they have a weird problem where it would freeze on the first gameplay, even though everything’s already initialized. So I sent it to some of my friends and they’re getting no freezing, but the same problem I am. Why is this happening? How can I ensure it will work fine for everyone all the time. I didn’t change anything for days, and then it suddenly stopped working, which makes no sense. We’re also all on Macs using Safari and the latest version of Flash, so I don’t see why there is any difference at all