Can anyone help me with the following?

When I do an emerge -s flex, I get
*  sys-devel/flex
      Latest version available: 2.5.4a-r4
      Latest version installed: 2.5.4a-r4
      Homepage: http://www.gnu.org/software/flex/flex.html
      Description: GNU lexical analyser generator

There is an -r5 ebuild in the portage dir. and this version is not masked, 
so why isn't it listed in the search?

Almost the same with the xfree-4.2.1.ebuild. This one is masked but if I 
unmask it, I still get the 4.2.0-r12 version listed.

When i try to give the 4.2.1 ebuild on the emerge command line I get the 
following:
These are the packages that I would merge, in order.

Calculating dependencies |

emerge: all ebuilds that could satisfy ">=sys-devel/flex-2.5.4a-r5" (from 
ebuild / x11-base/xfree-4.2.1 merge) have been masked.

I am confused. What does that mean and where is it masked?

-Rolf