Internal server error after saving an invoice

Has anybody had an issue like this. I can create an invoice, but when I hit “Save” I get the following:

Forbidden

You don't have permission to access /suitecrm/index.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

The permissions on index.php are 755 for the same user and group that uses the rest of the app.

Any ideas.

This is for SuiteCRM 7.2 on PHP 5.3.

It seems security suite settings might be restricting some module which is being used during save.