I have found an issue, but don't know how to fix it. If I reboot the computer, then open and render the file, it will render the file just fine. Everything will work. Then when I go to save the file, It hangs up. If I restart xLights, and reload the sequence and try to render or save, it hangs up. Only when I reboot the computer and then open the file and render, will it do so. Really odd. I have 16 GB of memory and 14 is free, so that isn't the issue....
How long have you left it when it hangs??
Is it still trying to save your file, or has it got to the render stage??
Only asking as I have read elsewhere that it may be one of your effects taking a long time to 'sort itself out'