@k9vet

You have effectively duplicated your post here.

Please do not do this. If you wish to add information to your original post that is more helpful than possibly splitting suggestions that may be the cause or not and reduce the possibility of duplicate suggestions that do not work.

You have also been asked quite a few times now to put your complete computer specs into your signature which you can do in your profile area. Without that information, a list of which can be found here, we can't really diagnose the root of your problems.

Doing all of the above may increase participation from other users who might otherwise not get involved.

Most of the time a setting may need changing or a driver may need updating in the operating system.

You say many clips are in use. What does task manager show when trying to play the project? How much physical memory is reported to be in use? If it exceeds the total amount of physical ram in your system that could be one possible cause for the lockup but only could be. We need more information. Are the clips on multiple tracks or just one?

Please also try to give screen shots of the timeline and program settings. We do not have access to your machine so we can only guess at what causes this. It could be many things or one specific thing.

How long is the project? What resolutions are you working at? Are you mixing clips from different sources? Are the file codecs in use the same? Do any of the clips involve variable frame rates? Are you using any of the programs or third party plugins? If so which ones and how many instances of them are running? Have you tried to use proxy files first? What are your audio settings in the Program settings set to? How many separate audio and video tracks are in use?

Yes I have gone over the top with the questions but any one of those could lead to an answer or solution.

Ray.