"The GPU-accelerated ray-traced 3D renderer does not have enough free video memory"

I've just updated my AE to 12.1 and it fixed the crashing problem on OSX 10.9 perfectly. But every time I open the software it shows: "The GPU-accelerated ray-traced 3D renderer does not have enough free video memory (VRAM) to operate. The renderer will use the CPU. To allow the ray-traced 3D renderer to use the GPU, close other applications and restart After Effects." This never occured before (even when it's still 12.0.1 on Mavericks) and nothing changed after I restarted the Mac. I've installed the latest version of CUDA (5.5.28) and my device is 15.4" Macbook pro with retina (16G RAM, 512G SSD and Nvida GTX 650M)

Thanks a lot