[F8] loadMovieNum problem

Hello there.
I'm new here, but I've got this problem with a sequence of swfs at my work.
The movie is a twist-a-plot, choose-your-path story with code attached to buttons to 'loadMovieNum' the next swf of your choice (I did not code this - it's something inherited from the previous designer!).
However, at 'scene9.swf' all I get is a white square where the next clip should load. I tried everything I could think of - adding the full path name, checking that the files are actually up on the server (it works locally), saving as previous versions of Flash.
And here was where I made an unhelpful discovery - having saved the first file in the sequence as a Flash MX file, I re-saved it as Flash8. Suddenly that file won't load the NEXT swf.
So... Is anyone aware of the changes that are made to a file if you save to MX and then back to Flash8 that might cause it not to 'loadMovieNum'? What have I lost by reverting and then upgrading to Flash 8 again?
Any help appreciated.

Double post deleted

Well, I probably didn't explain my question too well...
Basically I'm wondering why a bit of 'loadMovieNum(...)' code would stop working when you save the file as FlashMX and then back as Flash8.
Everything LOOKS the same, code-wise.
Anyone had a similar problem? Any ideas hugely appreciated!
Cheers.