Thread:Project:Support desk/Special:Upload - Argument 2 is not an array/reply (2)

Solved. Thanks for the heads up. I discovered the line "$wgFileBlacklist = true" in my LocalSettings.php file, which must have been lurking there without problems, since WM 1.6. Commenting it out resolved the issue. Of course $wgFileBlacklist should never take the value "true".