Getting 500 error with Apache on Ubuntu

I have Ubuntu Dapper Drake (from the LAMP install cd) on my server. I
installed rails, and it works fine with WEBrick on port 3000. I have
followed many different resources online (including one at the wiki)
for getting it to work with Apache, with no luck. Part of the problem
is that they assume you will have one rails project on the whole
server. I want perhaps multiple projects, as well as a PHP project
already on there. If I go to I get the
welcome page is just a 500
error. If I run WEBrick, works fine.
If I run ./dispatch.fcgi from the command line I get the HTML code for
a 500 error page. Any ideas?