Wait - there's one more detail: The tween has an ease with an intermediate handle that creates an inflection, as shown in the image. Notice that most of the tween is highlighted in preparation for making that interval into individual keyframes - but pressing F6 causes Flash to crash. I've tried this on both CS5.5 and CS5 on separate computers with separate licenses installed with identical results - Flash either crashes on this simple task, or completely bungles the attempt and will crash on an attempt to close the file, delivering this error:
"Exception thrown in destructor (f:\dd\vctools\vc7libs\ship\atmlfc\src\mfc\winfrm.cpp:143) Encountered an improper argument" - smells like overflow overwrite error.
Found this one the other day while animating a character - set it up yourself and see! Create a graphic symbol, move & rotate it a bit over a classic tween of some interval of your choosing. Give the tween an ease-in, then edit the tween curve by inserting an intermediate point and manipulating the curve handles. Once you've OK'd that, select an interval that includes the frames containing the intermediate point (save your work!), press F6 and watch Flash get a slack-jawed glassy stare.
Yep, I tried it on good ol' CS3 - with no problems. Don'cha just love it?
I can't reproduce your crash. Can you please send me the file up to the point where you saved? Please zip the file, change .zip extension to .zzz, email the attachment to my attention at FlashAuthBetaBugs@adobe.com.
Flash Pro, QE
Thank you for the file. I can reproduce this issue. I have submitted your file for further investigation. Good catch!