Thank you very much Whirly.
Yes, I'm using the EEP-RC 6.4.0.527723 (64bit) an the skies don't look good at all.
I think I will go back to the default release viewer because I havn't manage to create such beautiful skies with my current viewer. I have a lot of skies in my inventory, so i'm going to note the settings before changing the viewer and I will try to recreate them on the default viewer.
I hope the EEP viewer will be improved because SL with no magic skies becomes less interesting for me
Thanks again for your help!