I signed up just to reply to this ancient topic. because it mirrored my hardware/software setup and i had the same issues. But i had a shred of luck and all my problems where solved and wanted to help others in my predicament... get a powerful computer to run the software or at very least... turn off the extruder travel real-time monitor. This process of reading the g-code and drawing it on screen and sending it to the printer caused a MASSIVE memory leak and ment steps were being skipped towards the printer, causing the choking. I click on g-code or any other view in that pane and instantly my printer takes 3 viagras and runs silky smooth and fast!