> According to the specifications of ISO 9660 
> (http://en.wikipedia.org/wiki/ISO_9660) only upper case 
> letters, numbers and underscore are permitted. Is this a 
> bug

This is clearly a bug (at least, a misinterpretation of the 
standard). I must have mixed joliet/iso9660 specs, causing 
the current ISO9660 restrictions to be too loose.

I'll fix that soon! (added on the TODO list)