I find some of the Effects, and Text, in particular, do tend to cause some 'freezes' with IFX v4.x which is a shame, but it used to be a bit 'flaky' with OS3.9 BB2 anyway. Save often and then you can always load a file that's part done back in again and finish what you're attemtping to achieve - with a bit of good luck.

I tend to use IFX v4.0 more than v4.5 Studio as v4.0 always seemed to be more stable for me, unless there's something that only v4.5 will do. Others may get different 'mileage' out of their system and depending on what needs they have.