This topic is so long ago.
I encountered the same problem, following the lynda.com Flash CS5 Essential Training
Looks like no one else here?
Oh man, I had the same problem!
After searching online for an answer, I found NOTHING that actually helps.
It wasn't until Flash crashed (which is 'another' wonderful feature courtesy of Adobe) and I had to restart my project
that I realized how to fix this issue.
Try just moving some of the points in between the two outer points.
Some of the tutorials I've read say that if the tweens are too difficult, then the hints wont work as well, even if flash is saying they are lined up correctly and turn green/yellow like they are suppose to.
I think by adjusting the inner shape hints' positions, it puts the animation in a slightly easier path to tween.
I hope this helps, it sure helped me!