Jon,

Indeed, -dumbSched causes this problem to disappear. I have attached 
another cygcheck.out on the off chance that it will be helpful. When I 
wrote this file, all my Cygwin packages were up to date, and git-cola 
was executing OK (no hangs).

-- D.A.

On 1/16/2017 6:09 AM, Jon Turney wrote:
> On 14/01/2017 01:38, David Arnstein wrote:
>> My cygwin installation can display simple X11 clients such as xterm. A
>> complex client such as git-cola, launched from a remote RedHat Linux
>> machine, will cause all X11 windows under cygwin to become unresponsive.
>> Windows Task Manager says "not responding."
>>
>> This problem occurs with recent releases of Cygwin/X11. The attached
>> cygcheck.out indicates the last X11 version that works well: 1.18-4.1.
>> All other cygwin packages are up to date.
>
> Thanks for reporting this problem.
>
> Unfortunately, I couldn't reproduce it.
>
> However, I suspect this may be caused by switching to the smart
> scheduler by default in xorg-server 1.19.0-1.
>
> So, the first thing I'd suggest you try is adding -dumbSched to the X
> server options to see if this makes a difference (e.g. 'startxwin --
> -dumbSched'