Unity launcher icon now only launches TB, additional icon(s) open to control

The newest package(s) will only launch TB, a 2nd or even 3rd icon opens on the launcher that controls just that current open instance.

Seems related to the StartupWMClass= Thunderbird line in thunderbird.desktop. Have tried various other to no avail.
Removing the line completely returns launching & control back to the single pinned thunderbird.desktop icon
(may require a log out/in after editing .desktop to get expected behavior

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: thunderbird 14.0~b1+build2-0ubuntu1 [modified: usr/share/applications/thunderbird.desktop]
ProcVersionSignature: Ubuntu 3.4.0-5.11-generic 3.4.0
Uname: Linux 3.4.0-5-generic x86_64
NonfreeKernelModules: nvidia
AddonCompatCheckDisabled: False
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.25.
ApportVersion: 2.1.1-0ubuntu2
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: doug 1843 F.... pulseaudio
BuildID: 20120611170459
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xf6ffc000 irq 47'
   Mixer name : 'SigmaTel STAC9228'
   Components : 'HDA:83847616,10280209,00100201'
   Controls : 27
   Simple ctrls : 18
Channel: beta
Date: Tue Jun 12 10:29:16 2012
ForcedLayersAccel: False
IfupdownConfig:
 auto lo
 iface lo inet loopback
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120603)
IpRoute:
 default via 192.168.1.1 dev wlan0 proto static
 169.254.0.0/16 dev wlan0 scope link metric 1000
 192.168.1.0/24 dev wlan0 proto kernel scope link src 192.168.1.102 metric 9
PrefSources:
 /etc/thunderbird/syspref.js
 prefs.js
 user.js
Prefs:
 places.database.lastMaintenance: 1338783891 (prefs.js)
 extensions.lastAppVersion: "14.0" (prefs.js)
 network.cookie.prefsMigrated: true (prefs.js)
 places.history.expiration.transient_current_max_pages: 78899 (prefs.js)
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
Profiles: Profile0 (Default) - LastVersion=14.0/20120611170459
RelatedPackageVersions:
 rhythmbox-mozilla 2.97-0ubuntu2
 totem-mozilla 3.4.2-1ubuntu3
RunningIncompatibleAddons: False
SourcePackage: thunderbird
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/26/2008
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A15
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA15:bd12/26/2008:svnDellInc.:pnXPSM1330:pvr:rvnDellInc.:rn:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: XPS M1330
dmi.sys.vendor: Dell Inc.