Error: Invalid file extension: undefined

Hi,

When I want to add music (xxx.mp3), I've the message "Error: Invalid file extension: undefined". (by upload button or drag and drop)

I worked fine 3 days ago... And I've no modified anything.

I've restarted my server 2 times, and the problem is the same.

I have to upload music quickly, then if you have meet this problem, the solution is welcomed

Thank

Nico

Dedicaced server, Ubuntu 10.04LTS, Airtime 1.8.2