SassAndCoffee 1.1 currently doesn’t work on AppHarbor, and returns a 502 Gateway Error on the site. I’m working with the AppHarbor folks to fix this as soon as I can. Sorry about this!
On startup, we write out the V8 DLL to a temporary directory and call Assembly.Load to load it. Unfortunately, even though the write succeeds, the Load fails for some reason. On AppHarbor, we would always fall back to Jurassic, but in 1.1 I disabled this fallback because of performance issues (and because it made it harder to debug the V8 load failures).