First, make sure that AE is up to date and your system meets the minimum system requirements. Make sure that any scripts or plug-ins you have installed from 3rd party manufacturers are also up to date. Make sure your GPU drivers are current. If everything is up to date and your system is still crashing it's time to debug the project.
Start by creating a new composition called "test" the is 10 seconds long. Add a single 200 X 200 colored solid to the composition. Animate the position of the layer from the top right corner to the bottom left over then length of the comp. Add the comp to the render cue or the Adobe Media Encoder leaving all settings at their default values. Render.
If this "test" render fails then recheck everything in the first paragraph and then give us details of your system and your OS and maybe we can help.
If this "test" render works, then go to your composition that fails and select all the layers in the main comp and press the U key twice to reveal all of the modified properties of every layer. Start by turning off the fx switch in the timeline for the layer with the most complicated effect and try a test render. Keep turning off effects until you get a successful render.
If your composition is still crashing and it has compressed video, especially MPEG video or any compressed audio files turn them off in the timeline one at a time.
When you have found the problem come back to us with the details of your project and screenshots showing the problem the is causing the crash.
That is the only way we can possibly have any idea what is going on with your project.
There were bugs in Keylight that have been fixed in the latest updates. Try updating AE.
If you still have problems then use the Adobe Meida Encoder to render a production format copy of the original MTS file so you are working with a standard production codec instead of a compressed file.
Neither seems to be working unfortunatley, is there anything else I could do so that I don't lose the work? I could try rendering the MTS in Media Encoder again, can you suggest a format? I rendered in H.264 - High bitrate. Also I just switched the footage in AE to avoid having to redo the composition, could that be why it seems to be rendering without the composition? (Sorry I'm new to AE)
MP4 is highly compressed and not a good production format. Render a JPEG 2000 QuickTime. That's a visually lossless frame based codec.
Did not say if your AE is up-to-date.
Everything is up to date, I will try and render in JPEG 2000 QuickTime and I'll get back to you. Thank you
If you want a blue background behind your back or then you need to put a blue solid on the bottom layer. After Effects always renders an alpha channel. The composition background will never render. The only thing changing the background color of a composition does is change the edge behavior of semi transparent pixels when the color mode is set to pre-multiplied with Alpha. It's a useless exercise.
If you had set the color mode to millions plus alpha and straight alpha and rendered the JPEG 2000 you would have a transparent background that would show up in an editing or compositing app. A transparent background will always Display as black and a media player.
I strongly suggest you type rendering in the search help the field located in the top right corner of AE and study up on some of the excellent community resources on the subject. If you're going to be video you owe it to yourself to learn how video works.