>   I installed the nvidia cg package. And then I added the following entry
> to  the rosdep.yaml file in visualization_common.
>
>
>

This is blank, what's the entry?  In any case, I don't think it should
actually be a problem of rosdep fails to find/install cg.


> The make process for ogre_tools still fails for me like before (undefined
> symbol "_main").
>

I think the wrong-architecture errors you're getting are probably the root
of your problems.  It seems like your build environment may not be set up
correctly.

What do:
file /opt/local/lib/libboost_thread-mt.dylib

and:
gcc -v

output?

Josh