I have been using after effects for a while, but I have never encountered this problem before!
I am importing an Illustrator file, how I always have (Import File > Select File > select Composition with Layers > Import)
My Illustrator file is also correctly set up. Each asset that I want as a layer on after effects, is its own layer on illustrator - 5 layers total in this case.
I got some sort of RAM message, that I accidentally closed, and since then whenever I import an illustrator file (exactly as I have been doing before) it imports as a composition, but with no layers, simply as footage.
It is a very illustrator heavy file, but I am working on a relatively new Mac Book Pro (16 GB 1600 MHz DDR3).
What is going on, and how can I fix it?
Without more specific details and screenshots nobody can tell you much. Start by flushing out the AE caches and re-save your file in AI.