What follows is a possible solution for an access violation in FSUIPC that can suddenly appear.
Note: the symptoms look very similar to what is described in the “FSX fails to run after FSUIPC4 first installed” FAQ post. The problem is different in the sense that in that case it will happen before FSUIPC ran successfully for the very first while in the problem solved in this post it occurs after FSUIPC has been running successfully for some time already.
So the symptoms are:
- FSX reports “Flight simulator has detected a problem with a third party software program” where FSUIPC is mentioned as the third party add on
- If you choose to continue running FSUIPC from the above dialog FSX will crash
- No FSUIPC log was generated for this run
- In the simconnect logging there is nothing to be found about FSUIPC (please see in the FAQ how to turn on the simconnect logging)
- In the windows event logger for applications you will find an entry similar to:
Faulting application name: fsx.exe, version: 10.0.61637.0, time stamp: 0x46fadb14
Faulting module name: FSUIPC4.dll, version: 4.8.5.9, time stamp: 0x50f440c1
Exception code: 0xc0000005
Fault offset: 0x0001c2a4
Note: the fault offset will most likely be different for every different version of FSUIPC
- If you delete the FSUIPC.ini file the problem will not disappear (if it does then you have a different situation and the problem might be caused by the content of your ini file)
The problem is caused by MS Windows which suddenly incorrectly determines that FSUIPC should be corrected to make it run ok on your machine and in the process just makes it crash!
How to solve this problem (requires editing your registry, only do this if you know how that works and don’t blame me if things do not work at all after doing this):
1) Open regedit
2) Go to the key HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers
3) Delete the key "C:\\Games\\FSX\\fsx.exe"="$~ RUNASADMIN IgnoreFreeLibrary<FSUIPC4.dll>"
If the key does not exist or does not end with the “IgnoreFreeLibrary<FSUIPC4.dll>” then you have a different problem than described here…
4) If you would like to run FSX as an administrator you need to activate that again as you removed that in step 3.
Note 1: it could be that this problem is caused by switching to another application while FSX is loading (while the splashscreen is shown) although I’m not certain about this.
Note 2: it could be that this problem is Windows 8 specific but again I’m not sure.
Best, Marcel Fransen
[Originally posted in the old FAQ by user huppel (Marcel Fransen)]
Posted : November 5, 2025 1:23 pm
