Erractic browser behavior

Hi everyone, first time here. Hopefully someone has also experienced something similar.

I created my fla in CS5 using AS3 for button behavior and preloader. Mostly the movie does everything on the timeline old school style with very limited actionscript (as I'm not a programmer, this stuff boggles my mind).

I'm using swfobject 2.2 to deliver the file. It's a fairly big swf file (almost 5mgs) with quite a few images. This file size is probably a big no-no but there was no getting around that for this project.

Everything works fine except for the erratic button behavior. There are 4 main nav buttons and when first visiting the page they work fine. But upon revisiting the page they hang up. The browsers (tested in Firefox, Safari and IE) become very unresponsive. If I clear cache and refresh the browser they work okay again.

I've tried everything I can think of at this point to resolve this but the problem persists. Most recently I've disabled the internal caching in hopes this would provide a solution. Nada.

Not sure if it's an internal scripting issue, a size issue, caching, etc.

Hopefully someone has experienced erratic browser behavior in this fashion. I just don't have enough experience in Flash to zero in on the problem.

Thanks in advance for any help.