More rails oddities

I have a number of rails sites running on subdomains. One is the actual website (alpha.limeworking), and the others are for development. I’m concerned right now with chris.limeworking. If I copy the entire alpha into chris, it works just fine in chris. But then if I upload a different app directory into chris that I’ve been working on locally and which definitely runs just fine locally, I get an Application Error.

I’m very confused – I know it’s not my app directory, because that runs locally. I know it’s not anything else, because the alpha site runs on chris just fine. What does that leave?

Also, if anyone has any tips or references for debugging Application Errors, I would be very grateful. If I could just get some sort of useful error message I could maybe take a stab at it, but “Application Error” doesn’t tell me anything useful. My site is in production mode, btw.