Does that file still behave itself in version CC 2015?
(If you accidentally let the Creative Cloud app uninstall your old versions when you "updated" to CC 2015.3, you can install your old versions again. Old versions are quite useful for troubleshooting! This page has info on how to install old versions. Your CC subscription includes CS6, CC, CC 2014, CC 2015, and CC 2015.3 versions of After Effects. You can install all of them alongside each other.
I have the same problem.
Something happened in Dynamic Link. I have to end task the background service for After Effects 2015.3 twice and it will load the file. But I can't preview it once it opens or send a comp to Media Encoder. I've lost days on this.
Thanks for that.
The file seems to work fine in CC 2015.
Is 2015.3 not compatible with my system somehow?
No, it should work on your system. I was just asking for troubleshooting purposes (and to make sure you could keep working if you needed to while we tried to help get you sorted out).
I wonder if it has to do with your NVIDIA driver. There was an update released by NVIDIA yesterday, I think. You might give it a try.
If not, if you could post your full log somewhere and link us to it, that might be useful.