Inconsistant mask behavior

i’m working on an intro to a website, i’ve already used several masks in the intro and and familiar with them, but for some reason, when im ‘scrubbing’ the timeline everything works fine, but when i test the movie, it does show up at all. there is nothing else on that part of the screen at any part of the movie, so nothing is blocking it. is there any other thing i should try to trouble shoot this problem, or has anyone ever had this problem with inconsistancy between what you see in the test movie and what you see while editing? if so, please reply with any helpful information. thanks. debo

(also, i’m aware of what locking and unlocking the mask and layer does as far as viewing during editing)