What OS? Is AE up to date? There's not much info here that will help us help you. You can try opening AE and importing your project rather than opening it. Do so with the Caps Lock key on. You can try re-booting. You can try moving the source footage temporarily to another location in case footage is causing the problem. You could let us know if there are any error messages.
Ok thanks. Im running it on Windows 7 and yes it's up to date.
We need to know a lot more to help you. Please provide answers to the questions listed here: "FAQ: What information should I provide when asking a question on this forum?"
Also, if you're typing in all caps that you need help, then perhaps you should be contacting Adobe Technical Support, where you're guaranteed to get a response, rather than posting to a forum where people help out in their free time.