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[Sinon]

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[Anduril]

What troubleshooting have you attempted so far?
File check?
Delete Gameguard folder/"Fix Gameguard Errors"?
Disabling other programs such as Steam?
Checking for Graphics Driver updates?

[HentaiLolicon]

Just gameguard dectected some potential Apps for hack/cheat, even harmless app which is being started in fullscreen will cause that error . Try giving it a clean start-up right after booting.

[Anduril]

Corrupted files. They can pop up up suddenly or get missed on a single file check. Whenever I have to file check, I tend to do the official launcher file check then the Tweaker "Check for Old/Missing Files" just to be sure. It takes a bit of time, but this method has caught more than its fair share of potential file issues for me.