How full are your drives, alicow?
You need at least 15% free on every drive connected to your computer, including the boot drive. 20% is better.
If you need to clean up files and make space, do that first. Then try to open your project. If you get the same error, try opening up the latest project file in your AutoSave Vault, and see if that will work. You may have lost some of the last of the work you did, but if your original project file is corrupt, it’s about the best you can do.
The AutoSave Vault is usually in your Final Cut Pro Documents folder on the main hard drive, but it is something that’s relocatable, so it might be easiest to do a Finder level search for “AutoSave” to find it.
Post back if that doesn’t help. Another option is your project grew to be too huge for the RAM you have, and the option there is to put in more RAM. If you post back, it would be very helpful if you included what version of the OS, FCP, QuickTime, how much RAM, what video card you have, all the system specs. Sometimes it’s tough to pinpoint problems without the vitals of the system.
debe