The versions of ember and handlebars you were using was off maybe? Not sure what Handlebars runtime is. I replaced them with the correct versions from builds.emberjs.com and now it works.
I ran into this problem today while migrating an older ember app. The problem is caused by mixing templates of type
If you compile your templates in production, then your build system is likely only bundling
However if you add some script
x-handlebars tags to your html, Ember will as part of its bootstrapping process look to precompile those templates. But without the full handlebars library it will fail at the
Solution: If you need the ability to compile handlebars while still using compiled templates, ensure that your build system contains the complete handlebars library, and not just the runtime.
Update for 2014 -
Ran into same error when I switched to cloudflare. This one was a real time suck to track down. Wish there had been a better message.
and error went away.