Interesting that this came up since I was going to post the similar/same thing where the entire desktop flashes black, except I'm on a Windows client with 4.1.2.2 connecting to Centos 7 systems running the same software mentioned by Joe. 
The nx-libs installed on the server side are 3.5.99.26-1.el7. 
I don't see a ~/.x2go/cache*  but ~/.x2go/<session dir>/cache* but they are all empty.
The only thing I see in the /etc/x2go/x2goagent.options is enabling the clipboard (X2GO_NXAGENT_DEFAULT_OPTIONS+=" -clipboard both")
I have enabled GLX on the server side to make some other applications happy, though the issue appeared with GLX on or off.
I've tried using the latest release of VcXsrv in my client but that didn't seem to make a difference.  

Given how Qt has issues already with some of x2go (I've needed to set QT_GRAPHICSSYSTEM to native for the menus to work reliably for some Qt4 applications) could Qt be contributing to the issue?

On Sun, Jan 30, 2022 at 2:40 AM Ulrich Sibiller <uli42@gmx.de> wrote:
Hmm, interesting. I have no idea how this could happen. Let's try to
narrow down the issue.

Some ideas:
- Please ensure you have the latest nx-libs (3.5.99.26) installed.
- Are you reconnecting or starting a new session?
- can you check if this issue stays when you are using another client?
Can you try to replicate it with a windows client?
- you could try an delete the nx cache on the client when no sessions
are running: ~/.x2go/cache-*
- you can run "x2goclient --debug" (but I doubt it will help with this issue)
- compare /etc/x2go/x2goagent.options on all server systems
- compare the session configurations for the different servers on your
client: ~/.x2goclient/

Uli

On Sun, Jan 30, 2022 at 1:21 AM Joe W <jsw140@hotmail.com> wrote:
>
> I use X2Go to connect from my local Linux system to some remote Centos 7 systems where I run Cadence Virtuoso software. As far as I know the systems and X2Go are set up the same.
>
> Systems have the latest OS patches.
>
> X2go was installed from Epel repo.
> client is v. 4.1.1.1-1.el7
> server is4.1.0.3-9.el7
>
> There is one system that I connect to where when I start the X2Go session then the screen goes black for a second or two.
>
> When I run Virtuoso on that system then whenever I click on the main Virtuoso window or a Virtuoso graphics window  then my screen goes black. If I click outside the Virtuoso window then the screen reappears. If I click on the Virtuoso library manager window then the screen stays on.
>
> Note that I am running X2Go windowed but my entire screen goes black, not just the X2go window.
>
> Any suggestions what could be going wrong and how to debug it? I do not know how to turn on debugging in the Linux version.
>
> I am wondering if it is something weird with the color palette since it only happens for certain windows.
>
> I can connect to other systems without issue that are set up the same.
>
> Thanks
> _______________________________________________
> x2go-user mailing list
> x2go-user@lists.x2go.org
> https://lists.x2go.org/listinfo/x2go-user
_______________________________________________
x2go-user mailing list
x2go-user@lists.x2go.org
https://lists.x2go.org/listinfo/x2go-user