OK, I have an update on this.
My hosting is FreeBSD 6.1, PHP 5.22 w/ Zend2, Suhosin Patch v0.9.6.2, and Apache 126.96.36.199. Given that WP 2.2.x works fine on this, I assume I'm meeting minimum requirements.
I have a test subdomain with an .htaccess file with the following contents to override my hosting defaults:
php_value memory_limit 32M
php_value post_max_size 16M
php_flag display_errors on
php_flag suhosin.cookie.encrypt Off
php_value suhosin.request.max_vars 2048
php_value suhosin.post.max_vars 2048
I'm trying to give php some more memory to work with as suggested elsewhere in WP support while getting suhosin to back off a bit: this is a vbulletin hack for the same sort of 500/blank screen issue. I have tested with default perms, recursive 644 and recursive 755 all with the same results. I tried with both a hand coded wp-config.php and a wordpress generated one.
After some teething problems with missing files where the php display errors helped out, I was back to a 500 Error. Checking the error logs it seems that Suhosin really doesn't like what wordpress is doing:
ALERT - canary mismatch on efree() - heap overflow detected (attacker '188.8.131.52', file '/hsphere/local/home/whetu/test.rawiriblundell.com/wp-includes/taxonomy.php', line 11)
[Wed Dec 26 18:32:27 2007] [error] [client 184.108.40.206] Premature end of script headers: /hsphere/local/home/whetu/test.rawiriblundell.com/index.php
Commenting out line 11 of wp-includes/taxonomy.php like so:
// $wp_taxonomies['category'] = (object) array('name' => ‘category’, ‘object_type’ => ‘post’, ‘hierarchical’ => true, ‘update_count_callback’ => ‘_update_post_term_count’);
will get wordpress installed and working, however it will be littered with errors. Removing the error display line from .htaccess will probably resolve this, however I doubt WP will function properly.
As far as this issue goes, the WordPress devs have dismissed it as not their problem:
Interestingly though, WP 2.2.x has exactly the same line of code in wp-includes/taxonomy.php yet WP 2.2.x appears to install and work fine. Note also that I have php 5.2.2 which should have the suhosin fix mentioned in the thread that the WP devs linked to when dismissing this problem. You may now raise one eyebrow and stroke your chin as if you are intruiged.
It's clear though, looking around WP support, that multiple people have this issue, and I bet that they're on different server configurations than me, and that like me, they or their hosting providers won't be entirely incompetent at setting up php with suhosin. So maybe this could warrant a closer look... or not.