Been running Ubuntu-Mate 18.04 LTS for a few months now with no problems. Keeping everything updated, etc. The last 2 weeks at Startup I get this: A box that's 3 5/8" wide and 1 5/8" high. It's mostly White in color w/a black header. Inside the White box it states: SYSTEM PROGRAM PROBLEM DETECTED, Do you want to report the problem now? And there is 2 option Buttons: Cancel w/a Red X and Report Problem.. I have always Reported the Problem..! Never heard or received any comments, etc...
Several users have the same issue. Please add the error message found in your System Tools to this report:
Simone; Hi..! I found the System Tools in Menu then I found the Log Viewer, that contains 26 actual Logs, which one should I be looking in for the Error Message...? I new to Mate...
We found our issue in apport.log.1. Please add your text to the other entry which I gave above. This allows the Q&A to find a pattern where to look for.
Here is what my apport.log.1 System Log Reported:
ERROR: apport (pid 5527) Thu Feb 28 13:14:52 2019: called for pid 1334, signal 11, core limit 0, dump mode 2
ERROR: apport (pid 5527) Thu Feb 28 13:14:52 2019: not creating core for pid with dump mode of 2
ERROR: apport (pid 5527) Thu Feb 28 13:14:52 2019: executable: /usr/sbin/lightdm (command line "lightdm --session-child 13 20")
ERROR: apport (pid 5527) Thu Feb 28 13:14:52 2019: is_closing_session(): no DBUS_SESSION_BUS_ADDRESS in environment
ERROR: apport (pid 5527) Thu Feb 28 13:14:53 2019: wrote report /var/crash/_usr_sbin_lightdm.0.crash, Here is this Files contents: /var/crash/_usr_sbin_lightdm.0.crash, I could not open it..?
Thanks, James. I have added your entry to the existing entry about lightdm error with UM 18.04.2
Hi @jimlp12,
In the other entry, @mdooley suggested to delete the crash log files in case the error is only a hoax which repeats itself only because of a crash log file.
My error message disappeared suddenly.
In case you have still that error, open Terminal and type pkexec caja .
This will open Caja as superuser.
Navigate to /var/crash.
Delete the log files in that folder.
When I entered that folder, I had no crash log file.
Actually Newhere, I did NOT say to delete crash log files. What I did say was to delete any files found in /var/crash. Just a small distinction.
If you are interested in that kind of thing, open Log File Viewer and look at apport.log and apport.log.1 which should let you see the actual crash logs.
Hello;
I have performed as instructed the directions contained in this email, afterwards, I re-Booted my laptop and the Error Message has disappeared.....! Thank you so much...! =)
Wonderful news. 
You can close this entry as solved.
In my case, the only file in the /var/crash folder, was the one I sent a copy to you a few days ago, I could not open it on my laptop, it required a special app...
I agree, If not I'll be contacting you or someone else there for assistance. Tonight as I opened a couple of other log files, just browsing, they opened in Libre Office Writer. A new window was open when I closed out /var/crash folders and Terminal, it said Libre Office could not find Jave Runtime Environment installed...? Do you know what Jre package would be ample for Libre Office..?
Yes, please close this topic, favorite & 1 that worked was from Newhere... =)
Does LibreOffice works fine when you open the program? If it works fine, then leave it as it is. You can break a program if you open files which have different code.
Log files have code which is not understood in an office program. Office Writer is made to open files made with code used in Word etc.
You can use System tools - Log viewer to read log files.
Newhere; Thanks..! I installed LiberOffice 6.1, Mate came w/LiberOffice 6.0 and I also installed JRE IBM version as recommended by AskUbuntu... it's fine now. Thanks again...