Thread:Extension talk:UploadLocal/Error "An unknown error occurred."/reply (2)

I had this error, the following 3 lines in LocalSettings.php did the trick: $wgMaxUploadSize = array(   '*' => 1024 * 1024 * 250  ); Which limits all uploads to 250MB. I would guess that OP did not use the right datatype for $wgMaxUploadSize.