Ross could you please try to reproduce this?

I'm not able to reproduce this. Hans are you using international characters in the playlist names you're creating? Have you specified a playlist director in server settings or not? 

The same happens both when using international characters in the playlist names and when not.
Yes, I´ve specified a playlist folder. The folder name seems to OK since the previously saved playlists are available when I do a complete rescan.

is the playlist folder writeable/executable for the slimserver user? new playlist are saved in the db, then written out to the drive.  however, it looks like there should be some sort of note in the log if it can't create a filehandle: 
$output = FileHandle->new($filename, "w") || do {
			msg("Could not open $filename for writing.\n");

I did chmod o+rwx to the playlist folder even this didn't solve the problem. Where can I find the log file?

Another comment. I know there is a logfile somewhere, I´ve checked it when I struggled with upgrade to 6.5.2 with Suse 10 but then I added the path to the log file as an argument. Is there a default logfile somewhere?

Anyway, if basic operations are not successful, such as reading/writing the playlist file, there should be some form of error message to the user, both from the Squeezebox and from the web interface. The log file may contain ADDITIONAL information but all serious errors should be visible to the user... 

To set up logging of file operations, go to Server Settings -> Debugging -> and make sure that d_source and some other options are checked.  I don't have the same version of Slimserver as you do at the moment, but I think there is a d_file and d_playlist that should be included as well.

On linux systems the log is available in /var/logs/slimserver

Hans have you had a chance to take another look?

This does not seem to happen in 7.0.  If someone sees otherwise please reopen.