How to decide Adoobe Illustrator problems

[ERMEGA]

I have Illustrator CC 17.1 and when I save a file as a .ai file, it saves it as an Adobe Illustrator Artwork 17.0 file. When I try to open the file later, I get a "file is in an unknown format and cannot be opened. " How do I fix this?

 

[ThrashZone]

Hi and welcome to SevenForums,
Not to deflect but cc has free already paid for included support :/
Have you asked Adobe ?
Cheers.