On the live-CD session, I tried installing Lubuntu double clicking on the install button on the desktop. Here, the CD starts running but then stops running and nothing happens.

Next, I rebooted and tried installing Lubuntu directly from the boot menu screen using forcepae again. After a while, I receive the following error message:

The installer encountered an unrecoverable error. A desktop session will now be run so that you may investigate the problem or try installing again.

Hitting Enter brings me to the desktop. For what errors should I search? And how?

Thanks for some hints!

On Lubuntu 12.04:

uname -a
Linux humboldt 3.2.0-67-generic #101-Ubuntu SMP Tue Jul 15 17:45:51 UTC 2014 i686 i686 i386 GNU/Linux

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 12.04.5 LTS
Release:    12.04
Codename:   precise

upowerd appears to hang:

Aug 25 10:53:28 lubuntu kernel: [  367.920272] INFO: task upowerd:3002 blocked for more than 120 seconds.
Aug 25 10:53:28 lubuntu kernel: [  367.920288]       Tainted: G S       C   3.13.0-32-generic #57-Ubuntu
Aug 25 10:53:28 lubuntu kernel: [  367.920294] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Aug 25 10:53:28 lubuntu kernel: [  367.920300] upowerd         D e21f9da0     0  3002      1 0x00000000
Aug 25 10:53:28 lubuntu kernel: [  367.920314]  e21f9dfc 00000086 f5ef7094 e21f9da0 c1050272 c1a8d540 c1920a00 00000000
Aug 25 10:53:28 lubuntu kernel: [  367.920333]  c1a8d540 c1920a00 d9e44da0 f5ef6540 c1129061 00000002 000001c1 0001c37b
Aug 25 10:53:28 lubuntu kernel: [  367.920351]  00000000 00000002 00000000 e2276240 00000000 00000040 c12b0ec5 c19975a8
Aug 25 10:53:28 lubuntu kernel: [  367.920368] Call Trace:
Aug 25 10:53:28 lubuntu kernel: [  367.920389]  [<c1050272>] ? kmap_atomic_prot+0x42/0x100
Aug 25 10:53:28 lubuntu kernel: [  367.920404]  [<c1129061>] ? get_page_from_freelist+0x2a1/0x600
Aug 25 10:53:28 lubuntu kernel: [  367.920417]  [<c12b0ec5>] ? process_measurement+0x65/0x240
Aug 25 10:53:28 lubuntu kernel: [  367.920432]  [<c1654c73>] schedule_preempt_disabled+0x23/0x60
Aug 25 10:53:28 lubuntu kernel: [  367.920443]  [<c16565bd>] __mutex_lock_slowpath+0x10d/0x171
Aug 25 10:53:28 lubuntu kernel: [  367.920454]  [<c1655aec>] mutex_lock+0x1c/0x28
Aug 25 10:53:28 lubuntu kernel: [  367.920478]  [<f857223a>] acpi_smbus_transaction+0x48/0x210 [sbshc]
Aug 25 10:53:28 lubuntu kernel: [  367.920489]  [<c11858e1>] ? do_last+0x1b1/0xf60
Aug 25 10:53:28 lubuntu kernel: [  367.920504]  [<f857242f>] acpi_smbus_read+0x2d/0x33 [sbshc]
Aug 25 10:53:28 lubuntu kernel: [  367.920520]  [<f881e0f1>] acpi_battery_get_state+0x74/0x8b [sbs]
Aug 25 10:53:28 lubuntu kernel: [  367.920535]  [<f881e8a9>] acpi_sbs_battery_get_property+0x2a/0x233 [sbs]
Aug 25 10:53:28 lubuntu kernel: [  367.920549]  [<c14fa61f>] power_supply_show_property+0x3f/0x240
Aug 25 10:53:28 lubuntu kernel: [  367.920561]  [<c114664f>] ? handle_mm_fault+0x64f/0x8d0
Aug 25 10:53:28 lubuntu kernel: [  367.920573]  [<c14fa5e0>] ? power_supply_store_property+0x60/0x60
Aug 25 10:53:28 lubuntu kernel: [  367.920586]  [<c1407d20>] ? dev_uevent_name+0x30/0x30
Aug 25 10:53:28 lubuntu kernel: [  367.920597]  [<c1407d38>] dev_attr_show+0x18/0x40
Aug 25 10:53:28 lubuntu kernel: [  367.920608]  [<c11dad15>] sysfs_seq_show+0xe5/0x1c0
Aug 25 10:53:28 lubuntu kernel: [  367.920621]  [<c119846e>] seq_read+0xce/0x370
Aug 25 10:53:28 lubuntu kernel: [  367.920633]  [<c11983a0>] ? seq_hlist_next_percpu+0x90/0x90
Aug 25 10:53:28 lubuntu kernel: [  367.920644]  [<c1179238>] vfs_read+0x78/0x140
Aug 25 10:53:28 lubuntu kernel: [  367.920654]  [<c11799a9>] SyS_read+0x49/0x90
Aug 25 10:53:28 lubuntu kernel: [  367.920667]  [<c165efcd>] sysenter_do_call+0x12/0x28

/var/log/installer/debug shows upower related error:

Ubiquity 2.18.8
Gtk-Message: Failed to load module "overlay-scrollbar"
Gtk-Message: Failed to load module "overlay-scrollbar"
ERROR:dbus.proxies:Introspect error on :1.23:/org/freedesktop/UPower: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
Exception in GTK frontend (invoking crash handler):
Traceback (most recent call last):
  File "/usr/lib/ubiquity/bin/ubiquity", line 636, in <module>
    main(oem_config)
  File "/usr/lib/ubiquity/bin/ubiquity", line 622, in main
    install(query=options.query)
  File "/usr/lib/ubiquity/bin/ubiquity", line 260, in install
    wizard = ui.Wizard(distro)
  File "/usr/lib/ubiquity/ubiquity/frontend/gtk_ui.py", line 290, in __init__
    mod.ui = mod.ui_class(mod.controller)
  File "/usr/lib/ubiquity/plugins/ubi-prepare.py", line 93, in __init__
    upower.setup_power_watch(self.prepare_power_source)
  File "/usr/lib/ubiquity/ubiquity/upower.py", line 21, in setup_power_watch
    power_state_changed()
  File "/usr/lib/ubiquity/ubiquity/upower.py", line 18, in power_state_changed
    not misc.get_prop(upower, UPOWER_PATH, 'OnBattery'))
  File "/usr/lib/ubiquity/ubiquity/misc.py", line 809, in get_prop
    return obj.Get(iface, prop, dbus_interface=dbus.PROPERTIES_IFACE)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 70, in __call__
    return self._proxy_method(*args, **keywords)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 651, in call_blocking
    message, timeout)