I have encountered a bug where using gradients sometimes randomly corrupts the illustrator file. When I open it I see the bug popup (yeah, I use Polish-localized version of Illustrator CC).
The bug report states something along:
Can't open the illustration. The illustration contains an invalid operation argument.
Offending Operator: Bd
Content:
%AI5_EndGradient
%AI5_BeginGradient:
I am using Windows 8.1. How can I recover my file?
You can follow the steps outlined in on that adobe page even though it states it's only for Illustrator CS2-CS5 it will work for CC as well.
The file location for Windows 8 is:
C:\Users\[ username ]\AppData\Roaming\Adobe\Adobe Illustrator 17 Settings\[localisation code]\[version]\
localisation code
for Poland will be pl_PL, but don't worry about that, there will most probably be just one folder in the Adobe Illustrator 17 Settings.
version
either x64 or x86, choose the one you are using
The file you are looking for has also localised name for Polish it's: Preferencje programu Adobe Illustrator
for other localisations it will be some translation of Adobe Illustrator Preferences
in section:
/aiFileFormat {
/PDFCompatibility 1
enableATEReadRecovery 0
/enableContentRecovery 0
/enableATEWriteRecovery 0
/clipboardPSLevel 3
}
Set the enableContentRecovery flag to 1 /enableContentRecovery 1
Then follow the "Starting Document Recovery" section from the link.
When you have the _[your filename].ai
file you need a huge text file editor so that you can remove offending operators. I have used 010 editor which has a 30 days trial.
Open the file and search (ctrl+F) for the offending content, it's a markup language so you have to remove whole sections between %AI5_BeginGradient: [your gradient name]
and %AI5_EndGradient
.
Rinse and repeat until it opens.