Using Ctrl-D to close the last bash session in Terminal leaves a defunct bash process and the terminal process consumes 100% CPU (on a single core).  The problem is consistent and repeatable.  A zombie only seems to results when it is the last tab to close; other tabs close and their bash instance goes away cleanly.   The Terminal processes respond to a simple kill and close.

The problem was not noticed until after I upgraded:
to xfdesktop 4.8.2 (from 4.8.1) to fix a problem with system shutdown 
to x11-drivers/nvidia-drivers-275.21 to fix new tab background drawing issue

Possibly similar to this ancient bug:
http://us.generation-nt.com/bug-354065-xfce4-terminal-lefts-zombie-processes-help-166371561.html


Relevant ps output (column 4 is CPU%):
chrisw    3547     1 94 08:43 ?        00:12:44 /usr/bin/Terminal
chrisw    3548  3547  0 08:43 ?        00:00:00  \_ [bash] <defunct>
chrisw    3334     1 98 07:45 ?        01:10:00 /usr/bin/Terminal
chrisw    3335  3334  0 07:45 ?        00:00:00  \_ [bash] <defunct>

Version information:
x11-terms/terminal-0.4.8

Other Xfce and related components:
app-shells/bash-4.1_p9
x11-libs/vte-0.28.1-r200
x11-themes/gtk-engines-xfce-2.8.1
xfce-base/exo-0.6.0
xfce-base/garcon-0.1.7
xfce-base/libxfce4menu-4.6.2
xfce-base/libxfce4ui-4.8.0
xfce-base/libxfce4util-4.8.1
xfce-base/libxfcegui4-4.8.1
xfce-base/thunar-1.2.1
xfce-base/xfce-utils-4.8.1
xfce-base/xfce4-panel-4.8.3
xfce-base/xfce4-session-4.8.1
xfce-base/xfce4-settings-4.8.1
xfce-base/xfconf-4.8.0
xfce-base/xfdesktop-4.8.2
xfce-base/xfwm4-4.8.1
xfce-extra/thunar-vfs-1.2.0
xfce-extra/thunar-volman-0.6.0
xfce-extra/xfce4-verve-plugin-1.0.0



Build tools information:
chrisw@newton ~ $ emerge --info
Portage 2.1.10.3 (default/linux/x86/10.0, gcc-4.4.5, glibc-2.12.2-r0, 2.6.39-gentoo-r3 i686)
=================================================================
System uname: Linux-2.6.39-gentoo-r3-i686-Intel-R-_Core-TM-_i7-2600_CPU_@_3.40GHz-with-gentoo-2.0.3
Timestamp of tree: Mon, 22 Aug 2011 16:45:01 +0000
distcc 3.1 i686-pc-linux-gnu [enabled]
app-shells/bash:          4.1_p9
dev-java/java-config:     2.1.11-r3
dev-lang/python:          2.6.6-r2, 2.7.1-r1, 3.1.3-r1
dev-util/cmake:           2.8.4-r1
dev-util/pkgconfig:       0.26
sys-apps/baselayout:      2.0.3
sys-apps/openrc:          0.8.3-r1
sys-apps/sandbox:         2.4
sys-devel/autoconf:       2.13::<unknown repository>, 2.68
sys-devel/automake:       1.7.9-r2, 1.8.5-r4, 1.9.6-r3, 1.10.3, 1.11.1
sys-devel/binutils:       2.20.1-r1
sys-devel/gcc:            4.3.4, 4.4.5
sys-devel/gcc-config:     1.4.1-r1
sys-devel/libtool:        2.4-r1
sys-devel/make:           3.82
sys-kernel/linux-headers: 2.6.36.1 (virtual/os-headers)
sys-libs/glibc:           2.12.2