Unable to download files using WebDAV

Hi,
I am testing eZ Teamroom + WebDAV access. I am able to upload files but when I try to download a file, I get an "500 Internal Server Error" and the following error message in Apache log file:

[Fri Sep 24 17:59:55 2010] [error] [client x.x.x.x] PHP Fatal error: Call to a member function attribute() on a non-object in /homelocal/ezpublish/www/kernel/private/classes/webdav/ezwebdavcontentbackend.php on line 1449

My setup:
- eZ Publish 4.3.0 (plain_site package using eng-GB langage)
- eZ Teamroom 1.1-0 (I get the same error with latest SVN code: 1.1 branch).
- PHP 5.2.10
- Webdav client : konqueror or cadaver
- default WebDAV configuration (I have just set "EnableWebDAV=true" in ini file)

Thanks in advance,
Mathieu