My hosting provider is currently out of services.
Skins download is not possible until they fix the issue.
Sorry for the convenience.
I’ll keep this post updated until the problem is solved.
EDIT 06/04/2011 11:50 GMT+1 : my provider informed me that the DNS server is now repaired. DNS propagation should be finished in few minutes.
EDIT 06/04/2011 12:10 GMT+1 : it seems fully operationnal now. I added an alternate skin server to my apps to avoid such issue next time the provider will fail.