print tray icon disappeared just when clicking it

I was printing a document, which was taking very long as per bug #1262308

I clicked on the printer tray icon in the notification area. An empty submenu unfolded for a fraction of a second and then immediately the printer icon disappeared, while the printer was still printing (a line every 10 seconds)

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: cups 1.6.2-1ubuntu5
ProcVersionSignature: Ubuntu 3.8.0-34.49-generic 3.8.13.12
Uname: Linux 3.8.0-34-generic x86_64
ApportVersion: 2.9.2-0ubuntu8.5
Architecture: amd64
CupsErrorLog:
 W [18/Dec/2013:00:57:25 +0100] CreateProfile failed: org.freedesktop.ColorManager.AlreadyExists:profile id 'HP_DeskJet_940C-Gray..' already exists
 W [18/Dec/2013:00:57:25 +0100] CreateProfile failed: org.freedesktop.ColorManager.AlreadyExists:profile id 'HP_DeskJet_940C-RGB..' already exists
Date: Wed Dec 18 19:13:57 2013
InstallationDate: Installed on 2013-10-11 (68 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
Lpstat: device for HP_DeskJet_940C: hp:/usb/DeskJet_940C?serial=MY17O671S5BH
MachineType: Acer Aspire V3-571G
MarkForUpload: True
Papersize: a4
PpdFiles: HP_DeskJet_940C: HP Deskjet 940c, hpcups 3.13.3
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-34-generic root=UUID=5830b30e-69e8-4bb4-8a2b-bc2b43c7414a ro quiet splash vt.handoff=7
SourcePackage: cups
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/15/2012
dmi.bios.vendor: Acer
dmi.bios.version: V2.07
dmi.board.asset.tag: Type2 - Board Asset Tag
dmi.board.name: VA50_HC_CR
dmi.board.vendor: Acer
dmi.board.version: Type2 - Board Version
dmi.chassis.type: 10
dmi.chassis.vendor: Acer
dmi.chassis.version: V2.07
dmi.modalias: dmi:bvnAcer:bvrV2.07:bd10/15/2012:svnAcer:pnAspireV3-571G:pvrV2.07:rvnAcer:rnVA50_HC_CR:rvrType2-BoardVersion:cvnAcer:ct10:cvrV2.07:
dmi.product.name: Aspire V3-571G
dmi.product.version: V2.07
dmi.sys.vendor: Acer