Hello.
I have the same issue, style tab won't load while using Firestorm. It works fine with the SL viewer though.
I tried everything said here: reattaching, using a new copy, enabling media, clearing the cache, deleting the folders in App data, reinstalling Firestorm, adding dullahan_host.exe to my firewall, even using a different computer. Nothing works.
Any other thoughts? Thank you.