Not a plugin as I am been using the same plugins with the same theme for several weeks now without incident. I have also been using IE7 for a few months now, also without incident.
That being said I resolved the problem.
How I did it:
Went into file manager, located .htaccess file and edited by adding “SecFilterEngine off” without the quotes and then saved the changes. Works fine now, but for how long I don’t know.
I understand that HTTP 406 is a rare error and that it is usually created as a result of something that occurred on the webhoster’s end. Has anybody else heard that?