Hello Scott,
From the spip/ directory, I ran chmod -R a+rwx so that
read/write/execute is set on all files in the root and all
subdirectories.
So I understand you have an interactive session access to your server, not only
ftp.
At your suggestion, I created a PHP file and placed it in the
/spip/ecrire directory. You may view the results at
smferguson.com is coming soon. You may view this also.
No... I don't see it 
It answers: No input file specified.
but have you seen it? a long page with tables with diferent php config data.
Since I am not totally familiar with the environment requirements for
SPIP, I don't know what I am looking for, unfortunately.
It's clearly a PHP/Apache configuration problem (at least: after may come
PHP/MySQL interaction issues)
Your server seems to:
- at least properly start to execute php files (it deosn't serve php code as
text, but starts interpretation and come to errors),
- but can't access another file from a php file.
This may come from several origins in the Apache config (httpd.conf file and
others) and the mod_php integration (php.ini and others). For instance, there
may be several incompatible security protections.
Did you set up the server yourself? Do you know who did it? Are there other
applications running on the server?
SPIP expects to have a running http server with PHP and MySQL.
I suggest you first to finalise such a hosting and test it with basic unit
tests, before installing a full php application as SPIP. (You must make the php
include() function working).
Or switch to a form the shelf shared hosting.
How do you say "buena suerte" in Oglala Lakota language?
kindly,
daniel