Most "406 Not Acceptable" errors on websites are likely related to the mod_security setting on your InMotion Hosting account.

By default, all hosting accounts have mod_security turned on. There are some programs out there that do require mod_security to be turned off. If you do not disable mod_security it will cause a 406 error message. Mod_security can be turned off and on for each domain by request. If you would like mod_Security disabled you can email support@inmotionhosting.com to do so. If you send an email, for verification purposes please provide us with the original cPanel password, the current AMP password, or the last four digits of the current credit card on file.