Creating many MovieClips with 9-slice-scaling crashes flash movie

I was noticing that my scrolling lists (when scrolling quickly) would sometimes crash my flash movie.

After a lot of debugging I discovered it's only when the list items (which are movie clips) have 9-slice-scaling enabled. As the list scrolls, it's creating new list items and adding them to the container (while removing ones that scroll outside the container). Disabling 9-slice-scaling solves this problem (but leaves me with scaling issues).

Is there a reason why adding many MC's with 9-slice-scaling is crashing the flash movie?