Dispatch.fcgi not found despite being there

Firstly sorry if this is the wrong forum but I wasn’t sure which was the best to use!

I’m trying to install a rails app for the first time (I’m actually using ozimodo but I don’t think that makes any difference because it’s not even getting to the ruby stuff).

I’m running the software in a subdirectory of my main domain (www.draigwen.com/tumble). I’ve used the control panel to map this directory to the public directory of the rails app. dispatch* are all chmod’d to 755 as recommended in the wiki and I’ve made all the other suggested changes.

However I’m getting a 404 error when it’s trying to find dispatch.fcgi:

“The requested URL /home/…/ozimodo/public/dispatch.fcgi was not found on this server.”

(where the …'s are my username)

I’m pretty certain my .htaccess is altered as necessary. Since this is my first ever attempt to use something other than php I’m at a loss. Any idea what I’ve done wrong or failed to do?

Is there any further information I could give to help