Cygwin/X : display error with latest x-related packages

Dear Cygwin/X users and developpers,

I recently experienced a problem with a program using the X window system.
With the latest Cygwin release, the latter is not able to open the display, whereas with previous versions of cygwin (+ the x-window machinery, i.e the Cygwin/X installation as described in the installation notes, with xlaunch, xinit, xorg-server etc.) (prior to mid-February 2015), it was working correctly.
Other programs using the X window system, such as ghostview for example, is working correctly on my installation.
I have seen on the Cygwin/X news that X server and X.Org X11 packages have been upgraded to newer versions, and I was wondering if there was a known loss of backward compatibility with these fresh versions (even a simple change, like in the DISPLAY variable or something like that) ?

Best regards,
xflr6

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