The following string needs modifying:

#: C/totem.xml:925(para)
msgid ""
"The <guilabel>YouTube Browser</guilabel> plugin allows you to search and "
"browse <ulink type=\"http\" url=\"http://www.youtube.com/\">YouTube</ulink>, "
"and play YouTube videos directly in <application>Totem Movie Player</"
"application>. With the plugin enabled, choose "
"<menuchoice><shortcut><keycap>F9</keycap></shortcut><guimenu>View</"
"guimenu><guimenuitem>Sidebar</guimenuitem></menuchoice> or click on the "
"<guibutton>Sidebar</guibutton> button to show the sidebar. Select "
"<guilabel>YouTube</guilabel> from the drop-down list at the top of the "
"sidebar to display the <guilabel>YouTube</guilabel> sidebar."
msgstr ""
"O plug-in <guilabel>Navegador do YouTube</guilabel> permite que você "
"pesquise e navegue no <ulink type=\"http\" url=\"http://www.youtube.com/"
"\">YouTube</ulink>, e reproduza videos do YouTube diretamente no "
"<application>Reprodutor de filmes Totem</application>. Com o plug-in "
"habilitado, pressione <menuchoice><shortcut><keycap>F9</keycap></shortcut> e "
"escolha <guimenu>Ver</guimenu><guimenuitem>Barra lateral</guimenuitem></"
"menuchoice> ou clique no botão <guibutton>Barra lateral</guibutton> para "
"mostrar a barra lateral. Selecione <guilabel>YouTube</guilabel> na lista "
"suspensa no topo da barra lateral para exibir a barra lateral "
"<guilabel>YouTube</guilabel>."

the problem is the “e escolha” inside the <menuchoice> element: text isn't allowed inside a <menuchoice> element — see the original string.

The translation of the <menuchoice> element should be the following, with whatever appropriate text before and after it:

<menuchoice><shortcut><keycap>F9</keycap></shortcut><guimenu>Ver</guimenu><guimenuitem>Barra lateral</guimenuitem></menuchoice>