plasma-desktop hangs when USB storage inserted

I have it happen with two different types of USB storage (a normal 4GB Lexar stick, and an 8GB HTC phone).
Insert device, device notifier specifes that it is availalble, click to view in folder, and there is a hang.

The "hang" is of the panel (menu, taskbar, status panel etc.), apps still respond and can be switched with ALT-TAB. ALT-F2 run program is also hung.

If I go to a tty terminal (Alt-Ctrl-F1) I can see that the device has actually been mounted. A killall plasma-desktop and running plasma-desktop from the terminal brings things back to life (apart from ability to ALT-F2 start an app).

I have googled extensively for these symptoms but find little. The only reference is that the "automount" device notifier gets stick in an infinite loop but I'm pretty sure I'm not using that notifier but the standard KDE one.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: xorg 1:7.5+5ubuntu1
ProcVersionSignature: Ubuntu 2.6.32-23.37-generic 2.6.32.15+drm33.5
Uname: Linux 2.6.32-23-generic x86_64
NonfreeKernelModules: fglrx
Architecture: amd64
Date: Mon Jul 26 15:52:56 2010
MachineType: Dell Inc. Studio 1555
ProcCmdLine: root=UUID=2be78935-0f69-43ca-9fdb-6f90432ee8a8 ro quiet splash
ProcEnviron:
 LANGUAGE=
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
SourcePackage: xorg
Symptom: display
dmi.bios.date: 04/23/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A06
dmi.board.name: 0C234M
dmi.board.vendor: Dell Inc.
dmi.board.version: A06
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: A06
dmi.modalias: dmi:bvnDellInc.:bvrA06:bd04/23/2009:svnDellInc.:pnStudio1555:pvrA06:rvnDellInc.:rn0C234M:rvrA06:cvnDellInc.:ct8:cvrA06:
dmi.product.name: Studio 1555
dmi.product.version: A06
dmi.sys.vendor: Dell Inc.
system:
 distro: Ubuntu
 codename: lucid
 architecture: x86_64
 kernel: 2.6.32-23-generic