I have this problem from time to time. It seems to be caused by a process that is running in the background. If I access the Windows Task Manager when the engine is not running and then end a few processes then the engine will suddenly run. I have found, for example, that Windows Task Manager (under the Processes tab) that IExplorer.exe is running when, in fact, I do not have an intance of Internet Explorer running at all (i.e. no browser window is open). By ending this process A6 and SED will run perfectly. I am not sure why there is an IExplorer.exe process though. It could be a bug in IE or it could be some sort of virus or something. You might want to check for something like this on your system, though.