•What browsers and browser versions have you tested?
IE8 (unsupported) and Mozilla Firefox v22.0
•What exactly are you trying to save: CSS, Fonts, something else?
I was trying to save the appearance of the theme... the background...
•What is the link for the blog where you are seeing the problem happen?
Sorry, it is a private blog...
•Do you see any error messages?
No. Only the main page appears unformatted. The Posts and About pages appear correctly
•If you are able to view your browser's web console in the developer tools, do you see any errors show up there as soon as you click the "Save" button?
I don't use the developer tool.
I cleared the caché in both browsers, Temporary Internet files and temp files. I restarted my computer... and nothing!
This morning have tested this page in other PC and... it works!
I think it is a problem related with the proxy server of my company.
I will continue with my investigation...
Thanks for your help!