IIS Webdav 500.19 error on propfind

I finally got my webdav server accessible after a lot of trail-and-error runs ;)

However, some audio and video files cannot be played, while others can.

The log:

2013-06-13 13:44:40 192.168.1.150 PROPFIND /Profile/desktop.ini - 443 me 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 404 0 2 15
2013-06-13 13:44:40 192.168.1.150 PROPFIND /F/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:40 192.168.1.150 PROPFIND /F/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:40 192.168.1.150 PROPFIND /E/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:40 192.168.1.150 PROPFIND /E/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:40 192.168.1.150 PROPFIND /E/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:40 192.168.1.150 PROPFIND /E - 443 me 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 207 0 0 62
2013-06-13 13:44:40 192.168.1.150 PROPFIND /E/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:40 192.168.1.150 PROPFIND /E/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:41 192.168.1.150 PROPFIND /E/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:41 192.168.1.150 PROPFIND /E/desktop.ini - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15
2013-06-13 13:44:44 192.168.1.150 PROPFIND /E/Folder.jpg - 443 - 87.249.113.164 Microsoft-WebDAV-MiniRedir/6.1.7601 500 19 5 15

Some posts talk about a web.config problem, but i do not have that file??!!