<p>Running Mongrel 1.1.5 on Rails 2.1.2 using PostgreSQL 8.3 via ruby-pg 0.7.9 on OS X 10.4 server...</p>

<p>Added restful_authentication and exception_notification, the latter of which appears to be doing me no good when Mongrel simply dies with "Illegal instruction" every time I select /RESOURCE_NAME/new.</p>

<p>Doesn't matter what resource.</p>

<p>In development.log I see it's declaring its intent to render /layouts/RESOURCE_NAME.html.erb and then ... nothing. No stack trace, no anything. server.log is empty.</p>

<p>This is something of a showstopper and I'm not sure what to do. I tried running webbrick, a la:</p>

<p>script/server webbrick --force</p>

<p>But it ignores my wishes and loads mongrel anyway.</p>

<p>Any pointers would be appreciated.</p>

You probably want to create a "UNIQUE" constraint on the field "Domain" - this constraint will raise an error if you create two rows that have the same domain in the database. For an explanation, see
this tutorial in W3C school
-
http://www.w3schools.com/sql/sql_unique.asp
If this doesn't solve your problem, please clarify the database you have chosen to use (MySql?).
NOTE: This constraint is completely separate from your choice of PHP as a programming language, it is a SQL database definition thing. A huge advantage of expressing this constraint in SQL is that you can trust the database to preserve the constraint even when people import / export data from the database, your application is buggy or another application shares the database.