Migrating from Flash CS5 to CS5.5, now having a strange Error

Question

I migrated from CS5 to CS5.5 (on SnowLeopard). I wanted to make some changes on a small project (really simple), but even when I try to test the file without changes I get the following error:

VerifyError: Error #1053: Illegal override of createGeometry in flashx.textLayout.elements.FlowGroupElement. 

I never active call the FlowGroupElement, so I got absolutely no clue what is going on.

thanks for the help.