installation finished gracefully, but did not reboot when told to

Yesterday I ran saucy-desktop-amd64.iso in an Ubuntu Host running lubuntu-desktop with a not fully up to date 12.04.2 LTS.

(1) The installation proceeded as it should (it finished gracefully),

(2) I discovered, that the installed system boots to grub, but then nothing happens (only black screen in the virtual machine window).

So something seemed to be wrong. I looked more into it today.

A. I updated/upgraded the host operating system.

B. I zsynced saucy-desktop-amd64.iso (an received the next daily build).

And I tried again:

(1) The installation proceeded as it should (it finished gracefully), but *did not reboot* when told to. I had to shut down the virtual machine 'from the outside'. I think this is a bug.

(2) This time I could boot into a working installed Lubuntu 64-bit system with graphics and 'everything' works in the installed system.

The main VirtualBox specs are the following:
-----
VirtualBox version 4.1.12_Ubuntu_r77245

that comes with Ubuntu 12.04 (via the repos)

General:
Name: t1
OS Type: Ubuntu (64 bit)

System:
Base Memory: 1280 MB
Processors: 2
Execution Cap: 90%
Boot Order: Diskett, CD/DVD-ROM, Hårddisk
Acceleration: VT-x/AMD-V, Nested Paging, PAE/NX

Screen:
Video Memory: 12 MB
Remote Desktop Server: Disabled

Storage:
IDE control card
  IDE Primär master (CD/DVD): (1) saucy-desktop-amd64.iso (695,00 MB) at
installation; (2) Empty
SATA control card
  SATA-port 0: t1.vdi (Normal, 8,00 GB)

Audio:
Host Driver: PulseAudio
Controller: ICH AC97

Network:
Adapter 1: Intel PRO/1000 MT Desktop (Bridged adapter, eth1)

USB:
Shared folders

Description:
None
-----

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 3.11.0-7.13-generic 3.11.0
Uname: Linux 3.11.0-7-generic x86_64
ApportVersion: 2.12.1-0ubuntu4
Architecture: amd64
Date: Mon Sep 16 09:50:22 2013
InstallCmdLine: file=/cdrom/preseed/lubuntu.seed boot=casper only-ubiquity initrd=/casper/initrd.lz quiet splash --
InstallationDate: Installed on 2013-09-16 (0 days ago)
InstallationMedia: Lubuntu 13.10 "Saucy Salamander" - Alpha amd64 (20130915)
MarkForUpload: True
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)