Steps to Reproduce

This only happens in Firefox

1. Create a page titled ěščř
2. Attach Office files
3. Insert {viewfile} macro to view the attached Office files
4. Edit them
   
5. If it's Word document, it will open MS Word with a blank page
6. If it's Excel spreadsheet, it will pop up the following warning:
   

The same thing happens if the Office file name contains special character.

Workaround

• Use Internet Explorer
  IE will not work if you are using Office Connector 1.3.6 or lower due to WORDDV-102
  or,
• Rename the page title or file name