Attachments w/ Japanese characters

I’m using the /$file/ URL to launch the .xls attachment via a browser. The file name displays ok but I get a 404 in a new window. I can save the file to disk from Notes client but the file will not open. HOWEVER, a different .doc file w/ Japanese chars in the file name will launch from browser ok as well as from disk.

Are there certain chars to stay away from? I’ve got the JA language pack installed but could this be an encoding/code page issue?