From the nVidia driver readme:
(app-b) APPENDIX B: MINIMUM SOFTWARE REQUIREMENTS
o linux kernel 2.2.12 # cat /proc/version
o XFree86 4.0.1 # XFree86 -version
o Kernel modutils 2.1.121 # insmod -V
So in short, yes, you should upgrade from 3.3.6. I'd go with the newest, which is 4.2.1, but 4.2.0 should work too.