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Hi Wolfgang,

This just occurred for me too and I'm pretty sure the cause of this bug is the same as #1023604 that cripples F20.

Hi Patrick,
i don't know to fix it, can you please open a report at upstream?

thank you

*** Bug 1148206 has been marked as a duplicate of this bug. ***

Patrick, if i remember correctly, the fix for https://bugzilla.redhat.com/show_bug.cgi?id=1023604
was from you.

Yes, it was!
The fix did its job until you released 1.8.1-4, then the problem reappeared.
I tried looking further for an additional fix, but I feel this is an object reference counter problem (lack of increment or too many decrements) buried somewhere... very hard to track. I resigned :-/

Well 1.8.1-4-f20 was a bugfix for https://bugzilla.redhat.com/show_bug.cgi?id=1192722
and
https://bugzilla.redhat.com/show_bug.cgi?id=1203062
with
http://pkgs.fedoraproject.org/cgit/mate-panel.git/diff/mate-panel_notification-area-prevent-crash.patch?h=f20&id=30d7d28223f9d19120cd2c63ca08cafc1998f72a
from upstream
https://github.com/mate-desktop/mate-panel/commit/3f9eb20c55856f23cc841a75ac6d4fe5fba9bb9c
You can trys to revert this small commit in a local build to see if this really triggered the issue back in.
I don't use vnc so i never run in this issue and i can't reproduce it.
If this helps we have basic to discuss this at upstream.
As stacktraces from here and https://bugzilla.redhat.com/show_bug.cgi?id=1023604
really looks different i suggest to open a new report at upstream.

I'll try what you suggest and report here.
However the problem is not limited to vnc use.

Another user experienced a similar problem:

first login on a newly created user account on a newly installed f22 mate desktop 

reporter:       libreport-2.6.1
backtrace_rating: 4
cmdline:        mate-panel
crash_function: g_type_check_instance_is_fundamentally_a
executable:     /usr/bin/mate-panel
global_pid:     2281
kernel:         4.0.8-300.fc22.x86_64
package:        mate-panel-1.10.1-1.fc22
reason:         mate-panel killed by SIGSEGV
runlevel:       N 5
type:           CCpp
uid:            1001

@Wolfgang:
I reverted the "mate-panel_notification-area-prevent-crash" patch (on F20): 1023604 does not occur anymore. However F20 is EOL, but I do not yet use an F22 Mate computer intensively enough for a significant test for the current BZ. I would suggest someone with F22 computers removes this patch in the current version to test if it cures the current bug too.

Patrick,
the issue doesn't occurs on my machine, so i can't test your suggestion.
If you're sure that thr regression comes from  mate-panel_notification-area-prevent-crash commit, you should open a upstream report to discuss this.

Please test http://koji.fedoraproject.org/koji/taskinfo?taskID=11750807
Here i've revert the commit which was mentioned in https://bugzilla.redhat.com/show_bug.cgi?id=1238820#c17
But this can also bring back https://bugzilla.redhat.com/show_bug.cgi?id=1192722
If this build fix your issue than we have a base to discuss this at upstream.

Did anyone test my scratch builds?
Otherwise i assume you don't want that try to fix your problems.

Similar problem has been detected:

It happens at MATE session start-up.

reporter:       libreport-2.6.4
backtrace_rating: 4
cmdline:        mate-panel
crash_function: g_type_check_instance_is_fundamentally_a
executable:     /usr/bin/mate-panel
global_pid:     9635
kernel:         4.4.6-201.fc22.x86_64
package:        mate-panel-1.12.2-1.fc22
reason:         mate-panel killed by SIGSEGV
runlevel:       N 5
type:           CCpp
uid:            1000

New attempt from upstream to fix this issue.
Scratch build for all branches please test, as upstream and me couldn't reproduce the issue you help is needed.
f24
http://koji.fedoraproject.org/koji/taskinfo?taskID=14010315
f23
http://koji.fedoraproject.org/koji/taskinfo?taskID=14010343
f22
http://koji.fedoraproject.org/koji/taskinfo?taskID=14010355
epel7
http://koji.fedoraproject.org/koji/taskinfo?taskID=14010361

mate-panel-1.12.2-2.fc22 has been submitted as an update to Fedora 22. https://bodhi.fedoraproject.org/updates/FEDORA-2016-076da9244e

mate-panel-1.12.2-2.fc22 has been pushed to the Fedora 22 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2016-076da9244e

mate-panel-1.12.2-2.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.

Similar problem has been detected:

I have no idea how this occurred.  It happened right after I logged in to my system.

reporter:       libreport-2.6.4
backtrace_rating: 4
cmdline:        mate-panel --sm-client-id 10222479f27fc226ca138833148586649100000021260033
crash_function: g_type_check_instance_is_fundamentally_a
executable:     /usr/bin/mate-panel
global_pid:     2675
kernel:         4.4.13-200.fc22.x86_64
package:        mate-panel-1.12.2-2.fc22
reason:         mate-panel killed by SIGSEGV
runlevel:       N 5
type:           CCpp
uid:            1000