I was having this same issue.
I ended up fixing it by double checking my apache config, and it turned out I had AllowOverride set to none, instead of all.
I also had to copy/symlink a couple of javascript/css assets.
ln -s <scalr_home>/www/ui/js/extjs-4.0/resources/css/ext-all.css <scalr_home>/www/ui/js/extjs-4.0/resources/css/ext-all-2.css
ln -s <scalr_home>/www/ui/js/extjs-4.0/ext-all.js <scalr_home>/www/ui/js/extjs-4.0/ext-all-2.js