HI Sean, I have been following this thread with interest as I am also having problems - though my error message is slightly different. I have actually managed to install Silverstripe successfully but am getting error messages when viewing pages which say:
Warning: require_once(core/ManifestBuilder.php) [function.require-once]: failed to open stream: No such file or directory in /usr/local/psa/home/vhosts/jerseydoubleglazing.com/httpdocs/sapphire/core/Core.php on line 198
..which seems to be the same issue with the include path. The very strange part is that this issue is intermittent! Occasionally the site will work for a few pages but then the error will return. I have implemented the changes to Core.php as described in your ticket with no effect.
The output from your debugging code produces this output:
string(10) "before: .:" string(9) "after: .:"
..which is pretty minimal. But after multiple refreshes it sometimes (when it would be normally working I imagine) it produces this.
string(10) "before: .:" string(235) "after: /usr/local/psa/home/vhosts/jerseydoubleglazing.com/httpdocs/sapphire:/usr/local/psa/home/vhosts/jerseydoubleglazing.com/httpdocs/sapphire/parsers:/usr/local/psa/home/vhosts/jerseydoubleglazing.com/httpdocs/sapphire/thirdparty:.:"
I have also tried the alternative addition to the .htaccess file mentioned with no success either.
By-the-way the site works fine running on my Mac locally - the issue is when it is running on my shared hosting. Also when contacting my hosting company they thought I was mad to ask them to allow me to set the include path as they see this as a security risk. They said I would then be able to access other people's sites on the shared host and wondered why the paths were not set relatively. I dunno - it's all a bit above my head to be honest!
Anyway, any help would be greatly received. I am way behind my deadline on getting this website up and running and my normally good-natured client is starting to loose his patience!