Portage and packages.mask

I am trying to install the tango theme through portage but it just isnt happening. I am having problems with maskings. It asks for one to be unmasked, so I do, then it asks for another.
eg
I do

echo "=x11-themes/tango-icon-theme-0.7.1        ~*" >> /etc/portage/package.keywords

And I get this error

DhunEideann andy # emerge x11-themes/tango-icon-theme 
Calculating dependencies -
!!! All ebuilds that could satisfy ">=x11-misc/icon-naming-utils-0.7.0" have been masked.
!!! One of the following masked packages is required to complete your request:
- x11-misc/icon-naming-utils-0.7.0 (masked by: missing keyword)
- x11-misc/icon-naming-utils-0.7.1 (masked by: ~ppc keyword)

For more information, see MASKED PACKAGES section in the emerge man page or
refer to the Gentoo Handbook.
!!!    (dependency required by "x11-themes/tango-icon-theme-0.7.1" [ebuild])

So I do this:

echo "=x11-themes/tango-icon-theme-0.7.1        ~ppc" >>  /etc/portage/package.keywords

and get this.....

DhunEideann andy # emerge x11-themes/tango-icon-theme Calculating dependencies
!!! All ebuilds that could satisfy "x11-themes/tango-icon-theme" have been masked.
!!! One of the following masked packages is required to complete your request:
- x11-themes/tango-icon-theme-0.7.0 (masked by: missing keyword)
- x11-themes/tango-icon-theme-0.7.1 (masked by: missing keyword)

For more information, see MASKED PACKAGES section in the emerge man page or
refer to the Gentoo Handbook.

And it continues in a mega loop....

Help anyone?

But if you look a little more carefully, you'll notice the first "error" was telling you x11-misc/icon-naming-utils was masked by the ~ppc keyword, which means icon-naming-utils is a dependancy for tango-icon-theme, simply add both tango-icon-theme and icon-naming-utils (and any other packages that might complain) to /etc/portage/package.keywords and emerge away