Have you checked if your server has GD support for PHP? 

Yes I checked, and yes my server has GD support. So I guess this is not the problem ...

Thanks for your help. Any other ideas ?

What third party plugins are you using? What hosting are you using? Link for the site? What version of elgg are you using?

Rodolfo Hernandez

Arvixe/Elgg Community Liaison

What did you mean by third party plugin ?

I'm using this web hosting solution : http://www.ovh.co.uk/shared_hosting/shared_web_hosting_personal_25gb_traffic_unlimited_technical_sheet.xml 

I can't give you the link for the site but this is what I see :  http://hpics.li/12b0e73

I'm using elgg 1.7.10.

I just found something really weird : it works very well when I set the language into English (usually it's french), and when I set it back to French, it fails again ...

Well, how do you change language? May be that's the problem.

I said third party plugins because sometimes some of them interfered with the files plugin.

Rodolfo Hernandez
Arvixe/Elgg Community Liaison

@Sh:
"works... set the language into English.. when I set it back to French, it fails again..."
There is your problem cause ;)
There must  "something" in the fr lang file that is causing - maybe encoding issues.
Upload your fr lang file someplace i can grab and i will take a quick look.

@rjcalifornia:

I change language in the setting page (where you have account name settings, account password, email settings and language settings).

The group plugin use this file plugin too.

@DhrupDeScoop:

The fr lang file is the default one (encoding UTF8 without BOM) : http://sexiicookies.free.fr/Tung/fr.php

Thanks for your help guys

I found the solution : the problem was the file '/elgg/languages/fr.php' encoded in UTF-8. We just have to convert it into UTF-8 without BOM.

To do this, you can use Notepad ++ for example.