I am having the same problem, eli0s - I spent a few hours today tracking this bug down and have figured out how to reproduce it. I'm submitting an official bug report right now, but just for anyone who's searching around, here's how to reproduce (Release 147 only):
Create an empty project, add a sprite. Give it the effect "set color" and then the "water background" effect. ** Make sure "water background" is the second effect. ** Run the project and it crashes with the Assertion failure.
Not all effects cause the bug, but it seems like if a distortion effect is second on the list and a color effect is first, it happens. Sphere and Water Background are the two distortions I got the bug with, when combined with nearly any other effect.