After investigating the issue, we have come to the conclusion that this is actually an issue in the Flash Player plugin in Firefox. What this means is that we can’t fix the issue internally–we need to rely on either Mozilla or Adobe to fix this issue. We have filed bug reports with each company (links below) and hope they find a resolution quickly. If more people report occurrences, the priority will be elevated, so if you have time, please report that you are having trouble also. In the meantime, we suggest trying a different browser to see if you get better results. We have only been able to reproduce the issue in Windows 8.1 using Firefox 33, so we suggest switching to Chrome or IE until this issue is resolved.