Are you using proxies? What are your work area settings?
What, exact, version of AE are you using?
Hello Jessica Gomez,
Are you still facing this problem? If not, let us know how you solved it. If so, please let us know so we can assist you further.
Hey! I had this same problem, but think I solved it more or less.
I started using proxies for the first time today. I have a large project with many pre-compositions. I started turning each pre-composition into a proxy. I chose a pre-comp in the time line window, right clicked it>reveal layer source in project. Next, in the projects panel I right-clicked that original source file > create proxy > movie. The output/export setting seemed fine (Quality : Draft, Resolution: Half, Channels: RGB+Alpha, Quicktime animation, and so on). It worked for the first few proxies, but then I started getting an error:
"Current work area setting will cause the proxy to be out of synch with the original. To avoid this, set the work area start to the first frame of the comp."
If I clicked ok, it tried to create a proxy, but it seemed like the proxy didn't contain anything, or at least the timing was screwed up and it displayed the wrong part of my pre-compostion.
At first I turned off the sound in the export settings, and that worked once. Then I started getting the same error message again. I played around with the render settings until I switched "Time span" to "Length of comp" instead of "work area only". Can't say I fully understand why, but that seemed to fix my issue!