Adding preloader causing many errors

Hi,

I have a very elaborate flash project that works well when you load the .swf directly into the html page. However, once I added a prelaoder (using the show display progress code from “Essential ActionScript 3.0” example 28-8 which I’ve used successfully before) the .swf loads with a number of errors:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Scrollbar()
at flash.display::Sprite/constructChildren()
at flash.display::Sprite()
at flash.display::MovieClip()
at international_fla::MainTimeline()
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Scrollbar()
at flash.display::Sprite/constructChildren()
at flash.display::Sprite()
at flash.display::MovieClip()
at international_fla::MainTimeline()
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at international_fla::MainTimeline/initializeFlyerScrollbar()
at international_fla::MainTimeline/frame1()
http status: 0

There’s a lot of code in the file so I’m unsure what would be useful to post here. Does anyone know what would cause a preloading swf to cause a working swf to break like this?

The scrollbar that is referenced in the error code came from this site:

http://flashrevolution.net/actionscript-3-scrollbar/

…and like I said, it works fine without the preloader. Could I possibly need to import anything into the preloader’s actionscript?

I’m happy to post anything that might be relevant. Thanks in advance for any advice.