Did you try installing multiple themes before?It happened to me like 5 minutes ago. The "fix" I did was, deleting the systemData folder from the themes folder and extracting the home them again. It works again for me.
Just got my SX Core. I guess I was lucky enough to receive it in 3 days. Now all I need to do is find a person in the US who would install this for me.
@Xdqwerty, Its all about tech and it has an interesting story. Lain becomes obsessed with a virtual world called "The Wired" and that she tries to explore her true identity.