Forum:Uploading files

I can´t upload images in my Mediawiki. Loggued as sysop I´ve enabled uploading images by switching to true $wgEnableUploads in LocalSettings.php and also add $wgFileExtensions to admit jpg, etc. I changed the directory Images to CHMOD 777. The thing is that when I click "Upload file" I get a blank page (no http 404, or 500 or anything but blank) ¿Any clue of what could it be?