[chrishajer]

In testing this, the host, Dreamhost, suggested turning off mod_security, which was done, but the errors persist.

One thing I cannot understand: when accessing this URL:

http://harrismarine.co.nz/bbpress/topic.php?id=9&page=2

Sometimes it works, sometimes it does not. Sometimes it gives a 503 error, service not available. However, when that happens, the main site on the same server still loads fine:

http://harrismarine.co.nz/

Also, accessing this URL from another computer (at another location):

http://harrismarine.co.nz/bbpress/topic.php?id=9&page=2

is possible. So, why would a 503 error be served to some clients and not others, at the same time?