Just thought I should mention this while you are in the process of updating the plugin to a new version. Maybe the new CSS minifier in there will resolve this as well.
As soon as I turn on "Optimize CSS Code" I don't get the white screen people speak of, but instead the page load fails and returns "The connection was reset" in all browsers tested.
This seems to only happen on my local machine running a fairly recent version of WAMP. With legacy CSS minification implemented in htaccess all is fine, so it's no big deal, just wanted to put this info out there.
Thanks again for the plugin it's awesome!!