In eCart 6 and Data Bridge 1.1.7 and above we have added an option to change the preview engine. if you are experiencing problems with the default preview engine, open the WebAssist preferences panel, go to the preview section and try changing the preview engine to use one of the other options.
even with the preview disabled, the preview is still available. it will open in a browser window if you click the place holder.
I actually find this more helpful since it allows the wizard to work a little faster by not having to regenerate the preview, and viewing in the browser is a real size preview rather than the small snapshot