Gnarly permission issue using fcgi

deploying a Rails app for the first time on a mediatemple (dv) server
using capistrano and fcgi

everything looks OK but when I go to access the app, I get 500 errors
with things like

/usr/lib/ruby/1.8/fileutils.rb:1246:in `initialize’: Permission
denied -

these are for stylesheets (?!) - I looked at fileutils.rb and at that
line it is trying to open the file for writing, as part of copy_file().
If I make the file world-writable it just hangs up on the next one in
line. Why is it trying to copy the files anyway?

Surely the whole app doesn’t have to be writable by Apache, right? I was
following the otherwise excellent guide here

but it makes no mention of permissions issues.

Anyone have any idea what I screwed up?