[Wien] Xcrysden works for structure view, not for electron density display

[Luc Fruchter]

Dear all,

Xcrysden works fine from the w2web interface (run locally), when viewing 
a structure. So, I think it is correctly installed and configured.

However, it displays "requires X-Windows system ... Calc" when trying to 
use the "Calculate density with Xcrysden" button, or "requires X-Windows 
system ... Render" when I use the "Preview density button".

When I use the "Rhoplot" button, the density is correctly displayed (so 
the density file must be ok).

( I use latest versions for Wien2k and Xcrysden).

Thanks for any help.