I tried to do a render (less than 1000 parts and basically the same model and lighting as 20 or 30 similar renders I've done over the past few weeks) and the render started but has not completed. At the time I am posting this, the clock says the render has been running for over 12 hours. The progress indicator light is orange.

I then got fed up and went to a different model I was working on. I set up the lighting and camera but the render button was greyed out and could not be clicked. After some fiddeling and restarting of the page, I was able to click it and I got an error "Only one render allowed at a time." I cannot find a way to cancel the render that won't finish and I cannot render anything else until it does finish. However, it does not appear that any progress has amounted on it over 12 hours so I am not sure it will ever finish.

Is there a way to cancel a render so that I can move on?