R2013a slow when initializing

We run matlab remotely from a windows server to windows machine. Both sides are up to date and the configuration is the following:

• server with linux centOs 6.4-64bit, MGA200 drivers and license server for Matlab (not license.dat to check).
• windows7 64bit, with x-win32 2012 and a nVidia card.

we connect via ssh and export the GUI and launch matlab, then we get the splash screen and its desktop, then it freezes with "initializing/busy" for too much time.

With the -timing option I see that everything is loaded within 15secs but for some reason we are able to use the interface after very long time. This does not happen for R2012b

We checked/removed/kept the Java versions first to 6, then to 7, then both but this did not solve. Is there any way I can debug what's going on? Some wrapper? I have to add that if a I run a NX-like session everything is perfect, so something is wrong on the X export, I guess.

Thanks,

 alessio