My Adobe Illustrator is CS6 and it corrupts the file if I save it using accents

Question

My Adobe Illustrator is CS6 and it corrupts the file if I save it using accents. How do I fix this?
I mean, if I save a file called "crachá" I'm using an accent on "a" so it showed as "á" but if I do this Illustrator says the following error:
"The file may be read-only, or another user may have it open. Please save the document with a different name or in a different foulder"
and when I try to open it says:
"The file "Crachá.ai" is in an unknown format and cannot be opened."
So, my solution is to create a new file and call it "Cracha", without the accent. But it never happened before. How can I fix this legitimately?
Thanks.

Answer 1

As for the resolution problem: upsampling an image doesn't improve its quality, because there's simply not enough information there.
As for the warning you get: it's most likely caused by RGB color mode or by placed RGB content that interacts with other content in the file (e.g. because you applied transparency)
In English it's this one:
As far as I see it there's no alternative to learning the basics of printing, color management and transparency. This is nothing that can be done by some forum posts.
Printing:
http://rufus.deuchler.net/2011/06/adobe-publishes-a-new-creative-suite-555-printing-guide. html
You need to understand what's happening on conversion of RGB to CMYK color space, which will happen when printing to offset presses. When you print on office printers, something else happens and all kinds of color may come out, because these machines sometimes do their own color correction and everything depends on how you set up the machine.
Provided you check the PDF in Acrobat: you need to set up color management there as well. This might lead to the differences (greenish) you're seeing.
Find a good book on color management and read the manual:
Creative Suite * Understanding color management (there's more about the subject)
As for transparency:
http://partners.adobe.com/public/asn/en/print_resource_center/Transparency-DesignGuide.pdf
http://partners.adobe.com/public/asn/en/print_resource_center/TXPGuide.pdf
Before sending files to a print service provider you need to get information on how they need the file. Most providers won't accept PDFs generated with "No color conversion". Or they won't guarantee for the output.
What you see on your monitor won't necessarily match the printed result unless your system is correctly calibrated and color management set up. And even then there might be differences.
Can't you contact this former colleague, pay him an amount of money and let him teach you the tools of the trade?