The white screen is primarily due to the use of a dynamic style sheet which is generated with every page load. So instead of caching the style sheet, the theme generates a new one from the database each time.  This takes just a fraction of a second, but occassionally it may take long enough to see the unstyled content.

If you get to the point where you don't need to make any changes to the theme settings, you can change it over to a static style sheet. You would need to browse directly to the style.php file on your site and copy the contents of the page.  Then open style.css in your theme editor and paste the contents into that file after the content that's already there. Then save style.css.

You'll then need to edit functions.php.  If you go clear down to the bottom of the file, there's a function called mytheme_wp_head() that calls the style.php file into the header of the page.  Just change the style.php to style.css and that's it. But once you change to style.css, changing the theme settings won't have any effect.

I'll be releasing Flexibility3 soon, which uses a static style sheet, so if you want to wait until that comes out, you can do that too.