When you click on the ‘Programs’ button which will print out the list of programs, does the browser hang? If not, I think the issue is still browser compatibility — the ‘Preview’ uses certain features of HTML5 which may not be supported in all browsers. The other possibility is if the programs you set cause an excessive number of lines being plotted, that can cause the browser to hang. For example, a program that runs every minute can result in a large number of lines being plotted in preview. In any case you may want to reset the controller and start adding programs back one after another and check ‘Preview’ after adding each new program. This way you can pin-point the issue.