Impossible to upload file with Safari 6.0

Good afternoon!

Since I upgraded Safari to version 6.0 I am not anymore able to upload a file on a professional https website that I am supposed to use daily.

I can still access to the website thanks to a certificate that is still valid and I am also still able to download files from this website.

When I try to upload a file (csv file, 2 ko), the inner Safari file chooser pops-up (as usual) but all files are in grey shade. It is not possible to select any file, though I can move from one folder to another without any problem. The file can be .csv, .doc, .xls, it can be on my Mac, on a USB stick, on Dropbox, the problem is still the same : impossible to select it.

My colleagues who are still using Safari 5.16 did not meet this problem.

If you have any idea of how I can solve this problem, please let me know!

In advance, thanks a lot for your help!

Antoine