Your post sounds a lot like the problem underlying the several "undo isn't working" threads, but you've just noticed a lot more symptoms.
Try to open after effects with the option "run/open as Administrator". This option appears when making a right click on the program icon.
If that doesn't work, you might consider rolling back to the version of CC 2015 that was working for you. But, before you roll back, please follow the troubleshooting instructions in this post, so that Adobe can have some specific information on the problem so they can fix it in the next update!
We are very keen to isolate the causes of these issues. We have a couple of engineers visiting someone having this problem tomorrow so that they can debug the issue.
Please, submit detailed bug reports here:
If you provide your contact information, we'll be reaching out to some of you.
The issue is that the information held by the render thread is getting out of synch with the information held by the UI thread. This kind of problem can be worked around by either restarting the application or purging the caches---either of which forces a re-synchronization of these sets of information.
If you'd like to help us to test the After Effects CC 2015 (13.6.1) update---which fixes this bug---you can request access to the prerelease testing program here:
Choose the "Private programs" tab and click Apply to apply for the "After Effects CC 2015 (13.6.1) patch update" program.
Hi Todd. I've been using pre-release version 13.6.1 over the weekend and am very happy to report that it seems to be working very well!
I've not had ANY of the issues I reported in my original post.
Thanks for the support. It's good to see that Adobe do listen and are able to fix some of the major issues this quickly!
Thanks again, I'll report back if I notice anything else
The After Effects CC 2015 (13.6.1) bug-fix update is available. It fixes several bugs, including the one being discussed on this thread.
Let us know how things work after you have installed the update.