We recommend either the Chrome or Firefox browser for the best user experience with Gliffy as noted here: http://support.gliffy.com/entries/21406275-Browser-Minimum-Requirements-for-Gliffy-HTML5
We do not recommend using Internet Explorer, particularly for high-resolution exports. These will be grayed out in IE. Some large diagrams may be cropped when exporting over 100% in IE. To fully utilize the new exporting feature, we would suggest utilizing Firefox or Chrome.