and you may or may NOT find a topic here that specifically adresses the page youre having trouble with. Your missing the point -- its a file within wp-admin/
Im not going to argue with you .. you say youve looked, fine.
I. for one, cant help you any more than what Ive already said.
Lastly, though,, and this is ALSO covered in 1000 places, your .htaccess being chmod to 666 is a terrible security risk. Youre asking for trouble.
(And yes, I realize where you got that information, it doesnt mean its good advice)
If you need WordPress to make changes to it, you let it make them and then chmod the .htaccess BACK to a more secure permission setting.