Unknown error is detected - Unable to open file

[Fightinsquirrel]

File (ai) is on my disc and saving in the backgroudn is checked out. 

[Bill Silbert]

Please provide more details as to exactly what is happening. Is the problem with just an individual file or anything that you are trying to open? Is it a problem that has begun after an update to either Illustrator or your operating system?  Also please include the exact version of illustrator and the operating system that you are using.