X server problems with xscreensaver

[MR ZenWiz]

I am running Xubuntu 12.04 with xscreensaver version 5.15 (as it comes
from Synaptic), and I noticed that while the screensaver is running
and the screen is locked, when I type something or move the mouse to
unlock the screen, the input window remains behind the image - or so
it appears: the mouse only shows up within the bounds of where the
window would be, but it is not visible on the screen.

The screensaver I am using is GLSlideShow.

This only happens on my home desktop.  This did not happen on this
machine when I was running Ubuntu 10.10 about a month ago.

OS:	3.2.0-26-generic #41-Ubuntu SMP Thu Jun 14 17:49:24 UTC 2012
x86_64 x86_64 x86_64 GNU/Linux
	DISTRIB_ID=Ubuntu
	DISTRIB_RELEASE=12.04
	DISTRIB_CODENAME=precise
	DISTRIB_DESCRIPTION="Ubuntu 12.04 LTS"

(Relevant) Internal hardware:
M/B:	MSI 880G-e45 (MSI-7576)
CPU:	AMD Phenom II X6 1090T 3.2GHz
ram:	16GB Corsair DDR3 1333MHz (PC10600) 4x4G 9-9-9-24
vid:	ATI Radeon HD 4250 RS880 (on board)
f/w:	AMI BIOS V2.11 (12/08/2010)

xorg.conf (used to be the short one that comes with the release, but
this also doesn't help):

Section "ServerLayout"
	Identifier     "aticonfig Layout"
	Screen      0  "aticonfig-Screen[0]-0" 0 0
EndSection

Section "Module"
	Load  "glx"
EndSection

Section "Monitor"
	Identifier   "aticonfig-Monitor[0]-0"
	Option	    "VendorName" "ATI Proprietary Driver"
	Option	    "ModelName" "Generic Autodetecting Monitor"
	Option	    "DPMS" "true"
EndSection

Section "Device"
	Identifier  "aticonfig-Device[0]-0"
	Driver      "fglrx"
	BusID       "PCI:1:5:0"
EndSection

Section "Screen"
	Identifier "Default Screen"
	DefaultDepth     24
EndSection

Section "Screen"
	Identifier "aticonfig-Screen[0]-0"
	Device     "aticonfig-Device[0]-0"
	Monitor    "aticonfig-Monitor[0]-0"
	DefaultDepth     24
	SubSection "Display"
		Viewport   0 0
		Depth     24
	EndSubSection
EndSection

fglrx version is 2:8.960-0ubuntu1.

Should I file this as a bug?  I've also found a way to crash the X
server in this config, although it is tricky.

MR