My setup is the one suggested by the Wiki Threads. Initially (at the time when I re-created the subdomain), the symlink pointed directly from my applications public/ directory to the public_html_backup, but after playing around I decided to go back and create it from public_html. I created this one incorrectly (I believe it was to a subdirectory of my app's public/ directory), but I actually got an error with an Apache footer, with 403 Forbidden. Creating another symlink referencing public_html and a correct target yielded the first error again; this is my current situation.
I am wondering if I should drop/add the domain again to see if the domain will recognize the new symlink (it's still pointing to the same directory), or if I am just doing something incorrectly. I removed the second applications configuration from my .htaccess, but I will post that anyway. Thanks in advance for the help. The sub-domain in question is library.mydomain.com (guessing that the admins will be able to look up my real (not sneak-peek, though) domain).
.htaccess
# general apache options
# addhandler fastcgi-script .fcgi
addhandler cgi-script .cgi
options +followsymlinks +execcgi
# if you don't want rails to look in certain directories,
# use the following rewrite rules so that apache won't rewrite certain requests
#
# example:
# rewritecond %{request_uri} ^/notrails.*
# rewriterule .* - [l]
# rewritecond %{request_uri} ^/library.*
# rewriterule .* - [l]
# redirect all requests not available on the filesystem to rails
# by default the cgi dispatcher is used which is very slow
#
# for better performance replace the dispatcher with the fastcgi one
#
# example:
# rewriterule ^(.*)$ dispatch.fcgi [qsa,l]
rewriteengine on
# if your rails application is accessed via an alias directive,
# then you must also set the rewritebase in this htaccess file.
#
# example:
# alias /myrailsapp /path/to/myrailsapp/public
# rewritebase /myrailsapp
# rewritecond %{request_uri} ^/library.*
# rewriterule .* - [l]
rewriterule ^$ index.html [qsa]
rewriterule ^([^.]+)$ $1.html [qsa]
rewritecond %{request_filename} !-f
rewriterule ^(.*)$ dispatch.fcgi [qsa,l]
# in case rails experiences terminal errors
# instead of displaying this message you can supply a file here which will be rendered instead
#
# example:
# errordocument 500 /500.html
errordocument 500 /500.html
#errordocument 404 /404.html
errordocument 500 "<h2>application error</h2>rails application failed to start properly"
