I has been met this situation before, you could try to set "Default encoding when opening files" to ISO-8859-1, and restart code::blocks. Then, try to just open the specific file by code::blocks.
Or, you could convert all these invisible files from encoding "ISO-8859-1" to "UTF-8" through iconv program (Be Careful!!).
I don't know if this help, God Bless! :lol:
It seems that code::blocks recognize the ISO-8859-* as UTF-8 (when you set the default encoding to UTF-8), and there have some characters couldn't recognize by UTF-8 encoding, code::blocks sucks then.... ( Notepad++ will skip it off )