So, nobody else with this issue on Mac OS?
I re-installed the system (10.8.3) and Nuendo 6.0.2 and the problem persists: Nuendo GUI in 64 bit is missing elements related to shading and 3D effects.
To compare, I tried on a Mac mini with the same CPU as my MacBook Pro (Intel i7 I7-3615QM @ 2.3) and there’s no problem. The main difference between the mini and the MacBook Pro is that there’s one video card on the mini (Intel HD Graphics 4000) and there’s two on the MBP (Intel HD Graphics 4000 and NVIDIA GeForce GT 650M).
Could this dual video card be the culprit?