* REQUIRED: Non-printable characters were found in the 'functions.php' file. You may want to check this file for errors.
What are non-printable characters and how can I correct it?
They are characters that are non printable and should be removed. This is usually the first 32 ASCII characters + 127 ( it might also be extended characters above 127), for example character 7 is an "audible bell", so ya that's not going to work :)
Display (or web friendly) characters start at character 33, so look in your functions.php for some weird ASCII and delete them. Turn on debugging so you get a better error with the actual line call.
If you can't delete them you can use a
For reference on first 127 ASCII: http://www.telacommunications.com/nutshell/ascii.htm