It might help if we knew what the expression was and something about your comp.
This is the expression that is causing the crash:
[transform.xRotation, transform.yRotation, transform.zRotation]
I'm using it on a 3d shape layer pickwhipping the x,y and z position to the x,y and z of rotation. There is nothing else in the comp, no effects, no lother layers.
My imac is running 10.7.5 (3.1 Ghz Intel Core i5, 8gb RAM)
After Efffects version: 188.8.131.52
I've attached some screen grabs for reference.
I have also tried the same expression on After effects 5.5 (10.5.1.2) on same iMac and i have no problems.
I tried the same expression again but on a 15" mac book pro running 10.8.3 with AE cs6 (184.108.40.2068) and it crashed with same error.
Perhaps something to do with CS6 as I used this expression a couple of years ago in CS3 or 4.
That's a very odd use of an expression. It works just fine on my mac copy of CS6 and CC. It does generate some very odd movement as you animate rotation.
[transform.xRotation, transform.yRotation, transform.zRotation ]
Try allocating about a third of your ram to oher apps. At least 2 GB. I don't think that has anything do to with the problem but it make your system run a little smoother.