HAve you tried copying the timeline into a new blank file?
Yes, and the problem persists in the new file. I've also tried unzipping the FLA and running WinDIFF with an older copy of the file that doesn't exhibit the issue to see if I notice any obvious issues. The older working file begins having the same issues as soon as I add the missing page label to the last frame.
I can't post the file there, but this problem gets stranger.
I've narrowed it down to a particular text field on the 9th frame. There are two text fields on the frame (that's all), and if I remove the 2nd one, the problem vanishes. Now here's where it gets strange.
If I add the text field back by drawing a new text field, and pasting in the same text as before (copied from notepad first to ensure it's plain text), then the problem returns. But it only crashes on that specific text. It's like Flash doesn't like the specific content of the text field. If I change any single character, it doesn't crash! This is like some kind of bizzare easter egg.
I made a completely new file from scratch, recreated all the frame numbers, made absolutely sure that any text I copied into it was copied and pasted into notepad first, then copied from there before pasting the text into the new file
Here is the DOMDocument element that's causing the problem. It's not significantly different from any other text field element I've seen in the document, including the one on the same page as it, perhaps with the exception of the "a" value of the matrix tag.
<DOMDynamicText width="360.95" height="92">
<Matrix a="0.999862670898438" tx="62" ty="404.4"/>
2.) As a result
<DOMTextAttrs aliasText="false" autoKern="false" size="15" bitmapSize="300" face="ArialMT"/>
Here's where it gets REALLY messed up.
If I create the text field and type in the same exact list, same format, same numbering with a period followed by parenthesis, etc... it doesn't exhibit the problem until there's a 5th line of text. Prior to at least one character existing on the 5th line of text, there is no problem. Once I add a fifth line, however, the problem returns, even if it's just a single letter on the fifth line. I made a video of the behavior too, including where the window crashes and goes away.
If I add a 6th line to the text field, the problem goes away. It's like it has an issue with there being exactly 5 lines of text.
So here is the FLA file: http://www.filedropper.com/l027recreated. Seriously. Open it, it's on frame 9, label "p8". See the 2nd text field that has a list going from 1 to 3. First, try flipping back and forth between frames 8, 9, 10 to ensure there's no problem. Now edit the field to include "4.) whatever". Now flip between frames 8, 9, and 10 in the timeline again and watch it crash. Every time.
Try repeating this, but in addition to a line starting with "4.)" add another line with a "5.)". Now flip between the frames and see that it no longer crashes. It only crashes when there are 5 lines of text (the first line, plus the 4 numbered lines). It's very strange, and I can't figure out why it's happening.
Somehow, I feel that this is related to the crash bug where you make a brand new file, put an input text field there, edit it... press enter 10 times, then press backspace 10 times to empty the text, and flash CS6 will crash, every single time... only on "input" textfields though; not an issue if it's a "dynamic" textfield.
Here is a video of the problem occuring: http://www.filedropper.com/flashcrashbug
VLC's screen capture didn't pick up the mouse cursor, since I forgot to add the ":screen-mouse-image=(string)" option, but I'm only moving the mouse between the text I'm editing and the timeline frames. There's also a slight glitch at the end of the video that repeats showing the crash occur. There's no error messages, the window just closes without any kind of error message.