There's an upgrade for RhinoCam 1.0 for Rhino 4.0 on the Mecsoft website.

It says:

5 Axis indexed machining introduced in RhinoCAM SP1
2-10x improvement in performance in surface/poly-surface machining
Rhino crash when opening a new file after certain Rhino edit operations
V-carving gouging bug fixed

I've downloaded it, but have yet to try it.

Note that this is for those users who are using Rhino 4.0 and RhinoCam 1.0 for Rhino 4.0.

John