latex-beamer-3.00 cannot handle verbatim or lstlisting environments. Support for these two (and similar) environments was added in version 3.01. Please stabilize 3.01-r1 or 3.06-r1 including dependencies to dev-tex/xkeyval and dev-tex/pgf.
tetex-3 (which is stable on all arches beside mips) should include latex-beamer-3.01. The stable separate ebuild of latex-beamer is for tetex-2 only. There is a new latex-beamer-3.07 ebuild which installs on top of the tetex-3 included package. I think, I can close this bug as fixed now.