Recent upgrades to all hostgator.com shared and reseller servers have resulted in the Image Upload HTTP Error Fix plugin ceasing to work.
FIX: Uninstall/Deactivate Image Upload HTTP Error Fix.
The company has upgraded all of their servers to Apache 2.2.x, and mod_security 2. Because of this, the SecFilterEngine and SecFilterRemove statements placed in the .htaccess file will cause a 500 Internal Server Error, as they are no longer recognized by Apache2/mod_Sec2.
An associate of mine who works with HostGator has assured me that the majority of users should not be affected by the upload error, under the new mod_security rulesets. However, should a user experience a problem, sending an e-mail to HostGator support will result in a quick fix (whitelisting of the domain against the rule trigger).
NOTICE: This is an unofficaial posting. I have no authority to speak for HostGator, I'm just relaying information. (Yes, I do host there.)