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Does it create a data folder?  Try creating a data folder - it's strange that it doesn't have the ability to write.  I assume it also doesn't create an error.txt file with the full error.

No, no error.txt is created.

What happens if you just create the data folder and create profile.json file in it?  If you put in 

{
"enemyKnowledge": {}
}

as the body of the file, you'll have created the file it's trying to create.  

I found the problem. One file was still read only. Once I changed that everything ran like butter.

Awesome!  Runny butter :O

which file was that?