WP-Cache internal server error.

My blog works fine: https://www.bittbox.com
But when I enable WP-Cache, I get an “Internal Server Error”

“Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Apache/1.3.33 Server at https://www.bittbox.com Port 80″

This only happens when WP-Cache is enabled, and I have my wp-content folder writable by the server?

Any help is greatly appreciated.

~BittBox

every other click (only when clicking on the homepage)