Recently when logging into the StartCom control panel using FireFox I received the error pictured below. After some quick Googling, I was able to find a StartCom forum post from other users reporting the same issue. The following steps fixed the issue up for me. The fix for the error above is below. Please see picture below.
removing all ‘Software Security Device’s under node ‘StartCom Ltd.’, which is accessible in the tree view at Edit->Preferences->Advanced->Certificates->View Certificates->Authorities at node ‘StartCom Ltd.’