I've just pre-comped some layers and for some reason the effects on one of the layers ain't working. I can see the effect controls as I set them in the effects control panel, I can't see anything on the comp that might have switched the effects off... they just ain't working anymore.
It's pretty late here in the UK and I've been working a while so I might be missing something really basic (again) but I can't see what!
I'm still on CS3 for a few more months so I haven't used the new rotobrush yet, but based on the way rotoscoping usually works and how other AE brush tools work, perhaps there's a parameter you have to set to tell it the draw timing and, if not, it defaults to one second.
Just a guess since you didn't get any other answers ... sorry for the AE 101 type first answer and that I couldn't be more help ... you just said "the effects on one of the layers ain't working" and didn't mention you were using rotobrush so, considering the post is in the Basics Forum, I figured it might just be the effects switch.