this is there for debugging purposes. it shows you an error which has occurred in a script.

i recommend ignoring it unless you wrote the script by yourself. otherwise you can report this specific error as scripting bug.

You are probably using -showScriptErrors parameter, either in shortcut command line, or in Play withSix (or other game launcher) parameters.

I'm not using a launcher and I installed and started the game out of steam. there are no starting parameters.
I didn't add any script or modifications.

Can you please put a screenshot in here?
Is the window you're takling about in lower part of the screen or upper one?

There is a screenshot attached

It's a normal error script, it's enabled by default since ArmA 3 alpha and i wish it follow to be, so i voted down.

Okay, if everyone has it, than everything is alright :)

Yes it happens with me randomly

It's a script error report. Perfectly normal on the dev branch.