Aceville on "[Plugin: W3 Total Cache] Fatal error: Cannot use object of type W3_Config as array"

Hi, I am geting this error with a newsletter signup system called simple mailing. I want exclude this system - the pages and the files form wp-cache so it does not clash. Can you tell me how I can do this?

I have disabled everything I can find to disable to find what aspect of the plugin is clashing but even with everything disabled I am still getting this error.

Thanks, Bridget

http://wordpress.org/extend/plugins/w3-total-cache/