Make alt key work when using NX client on OSX to Ubuntu 10.04 host?

Question

I am using NX Client on Mac OS X 10.6 to access my Ubuntu 10.04 machine. I would like to use the Option/Alt key to Alt-Tab in the window manager and as the Meta key in Emacs.

Some searching on the internet suggests that I set my OSX ~/.Xmodmap file to:

keycode 66 = Alt_L
clear Mod1
add Mod1 = Alt_L Alt_R

Or:

clear Mod1
clear Mod2
keycode 63 = Mode_switch
keycode 66 = Meta_L
add Mod1 = Meta_L
add Mod2 = Mode_switch

Neither did the trick. Any suggestions?

Thanks!