TEXT file displayed as icon

All LOG files are displayed as icon and not as text.
The files are normal text file and can be open without problem, In the left top is wrote name of file. log Icon shell.
I try without success

  • disabled all the plug in except text plug in (latst one)
  • insert .log in preview text type file (in italian is : "Anteprima dei Tipi File Testuali"

If you make a copy of the files, keeping the extension the same, does that display OK?