Clean, default install (not upgrade)...
When trying to activate Hello Dolly plugin following error is received (followed by a cascading headers already sent error...)
Warning: in_array(): Wrong datatype for second argument in [path-clip]\wp-admin\plugins.php on line 9
Plugin is not activated. I tried the code edit mentioned here but that simply throws the error and stops loading the page. With untouched code, the error is thrown but the page load continues.