In my OS X training courses I always stress that using non-standard alphanumeric characters in folder and file names can cause a wide variety of problems. This includes characters like: ~!@#$%^&*()+={}[]\|;:/<>

Recently Gabe Higgins, one of All Covered’s helpdesk engineers, illustrated this point perfectly.

Gabe was working with a Mac user that was getting the error “Excel cannot open this workbook” when attempting to open Excel files off a mounted server volume. These files would however open fine if copied locally to the Desktop.

What Gabe discovered was that these files were stored in a folder (or subfolder) on the server that contained a | character (pipe). Initially this wasn’t self-apparent as the | character appeared to be a capitol i. Removing the | character from the folder name allowed these Excel file to open without the error.