It turned out to be a configuration problem at the webserver. The hosting company said "sorry, .htaccess permission was disabled for your site. They have been enabled"
For the benefit of anybody finding this thread in the future:
Setting PHP configuration settings from .htaccess is as simple as adding the line
php_value <name> <value>
or
php_flag <name> <on|off>
to an .htaccess file in your web directory.
Don DeCosta