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Users have raised questions about the errors that occur when launching or playing in Magic The Gathering Arena. Here are some solutions to get rid of the fatal error in the GC error message "GetThreadContext error".

How do you fix the fatal MTG Arena error in GC GetThreadContext Failed?
Disable DEP for MTG Arena in Windows 10
- Open Control Panel, go to System, then click Advanced system settings in the upper left corner.
- The system properties window should now be open.
- Go to the Advanced tab and click Settings in the Performance area.
- In the Performance window, go to the Data Execution Prevention tab
- Make sure to activate all the programs except the EPD I selected and click the Add button.
- In this last step, you have to navigate to the executable file of the application, select it and click on Apply.

Desinstalar el client FACEIT
FACEIT es una solución para que los clientes y servidores detecten a los tramposos en juegos o software en línea que podrían ayudar a los jugadores a romper las reglas mientras juegan.
If it is installed on your system, basically shut it down and try to start MTG Arena. If the problem persists, uninstall the FACEIT client, restart your computer, and try again.
You should be more successful this time.
Change compatibility mode to Win98 / ME
For those who don't know how to change compatibility:
- Right click on the game on Steam.
- Click Properties in the drop-down list (the last thing you have to click on).
- Click on the Local Files tab.
- Click on "Evaluate local files".
- Right click on the executable file "Cities.exe".
- Click on "Properties" in the drop-down menu.
- Click on the Compatibility tab.
- Check the box "Run this program in compatibility mode for:".
- Select "Windows 98 / Windows Me" from the drop-down list.
Add MTG Arena to your antivirus exception list
In many other cases where security fixes are at stake, these wonderfully legal apps could also get in the way. Users have reported that after updating their antivirus software, a fatal error suddenly appeared in GC GetThreadContext.
For some of them, it was as simple as putting MTG Arena on their VA's list of exceptions. Unfortunately, this does not always work. You may need to use other security software.
https://steamcommunity.com/app/363600/discussions/0/133260492058372519/
RECOMMENDED: Click here to fix Windows errors and get the most out of your system performance