murrine_style_draw_box: assertion failed

[Gablewatts]

Whenever I open the gnome-alsamixer when I have my USB headset plugged in the tab containing the controls for the USB headset had buttons that appear mangled and the following error messages are written to stdout/stderr:
** (gnome-alsamixer:25448): CRITICAL **: murrine_style_draw_box: assertion `height >= -1' failed
** (gnome-alsamixer:25448): CRITICAL **: murrine_style_draw_box: assertion `height >= -1' failed
** (gnome-alsamixer:25448): CRITICAL **: murrine_style_draw_box: assertion `height >= -1' failed
** (gnome-alsamixer:25448): CRITICAL **: murrine_style_draw_box: assertion `height >= -1' failed

Attached is a screenshot of how the mangled buttons appear.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: gnome-alsamixer 0.9.7~cvs.20060916.ds.1-2
ProcVersionSignature: Ubuntu 2.6.38-11.50-generic-pae 2.6.38.8
Uname: Linux 2.6.38-11-generic-pae i686
NonfreeKernelModules: wl
Architecture: i386
Date: Thu Sep 29 10:21:30 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, user)
 LANG=en_US.UTF-8
 LANGUAGE=en_US:en
SourcePackage: gnome-alsamixer
UpgradeStatus: No upgrade log present (probably fresh install)

[Gablewatts (gablewatts)]

I just noticed my first screenshot doesn't show the problem. I've discovered that as soon as you press the Alt key on the keyboard while the gnome-alsamixer tab is active, the tab redraws itself correctly.
So I'm attaching another screenshot that shows how the tab appears when it first opens.