I'm not sure about the error but suggest you update to he latest version - V 9.0.
It could be some other limit, (server setting) not related to Machform. What is the memory limit? Perhaps execution time 2800 is not allowed. 2800 (seconds) is 46 hours......surely that is not required! With error reporting on, are you seeing any PHP errors (or any others)? What about the server error log? If the process is timing out, there should be some indicator other than a blank screen.
Would suggest you submit a support ticket, since the Machform guys don't visit the forum that often, and the forum it not an official support source. Submit a ticket through your customer / billing area.