PHP-Error when uploading screenshot

[cologne]

i don´t know, where to post this issue... :-(

Successfully uploading screenshots in the Media Gallery:

F1_Nuerburgring-nocomeback.png successfully uploaded to album

I see these outputs from PHP on top of the following webpage:

Warning: fopen(/home/web/vdrift.net/public_html/Gallery/rss/mgmedia.rdf) [function.fopen]: failed to open stream: No such file or directory in /home/web/vdrift.net/public_html/Gallery/classes/feedcreator.class.php on line 684

Error creating feed file, please check write permissions.

Warning: chmod() [function.chmod]: No such file or directory in /home/web/vdrift.net/public_html/Gallery/maint/rssfeed.php on line 149