Comment 53 for bug 554079

Further to my comments #28, #29, and #30: to confirm, the issue appears to be unrelated to nvidia, xorg.conf, etc. Just had the same happen on my HP G60-530US Notebook. That machine is using:
*-display:0
             description: VGA compatible controller
             product: Mobile 4 Series Chipset Integrated Graphics Controller
             vendor: Intel Corporation

This machine also stopped at 71%. ssh'ing into the machine (as I did on the other) and looking at the processes shows:
$ ps -e
  PID TTY TIME CMD
    1 ? 00:00:00 init
    2 ? 00:00:00 kthreadd
    3 ? 00:00:00 migration/0
    4 ? 00:00:00 ksoftirqd/0
    5 ? 00:00:00 watchdog/0
    6 ? 00:00:00 migration/1
    7 ? 00:00:00 ksoftirqd/1
    8 ? 00:00:00 watchdog/1
    9 ? 00:00:00 events/0
   10 ? 00:00:00 events/1
   11 ? 00:00:00 cpuset
   12 ? 00:00:00 khelper
   13 ? 00:00:00 netns
   14 ? 00:00:00 async/mgr
   15 ? 00:00:00 pm
   17 ? 00:00:00 sync_supers
   18 ? 00:00:00 bdi-default
   19 ? 00:00:00 kintegrityd/0
   20 ? 00:00:00 kintegrityd/1
   21 ? 00:00:00 kblockd/0
   22 ? 00:00:00 kblockd/1
   23 ? 00:00:00 kacpid
   24 ? 00:00:00 kacpi_notify
   25 ? 00:00:00 kacpi_hotplug
   26 ? 00:00:00 ata/0
   27 ? 00:00:00 ata/1
   28 ? 00:00:00 ata_aux
   29 ? 00:00:00 ksuspend_usbd
   30 ? 00:00:00 khubd
   31 ? 00:00:00 kseriod
   32 ? 00:00:00 kmmcd
   35 ? 00:00:00 khungtaskd
   36 ? 00:00:00 kswapd0
   37 ? 00:00:00 ksmd
   38 ? 00:00:00 aio/0
   39 ? 00:00:00 aio/1
   40 ? 00:00:00 ecryptfs-kthrea
   41 ? 00:00:00 crypto/0
   42 ? 00:00:00 crypto/1
   45 ? 00:00:00 pciehpd
   54 ? 00:00:00 kstriped
   55 ? 00:00:00 kmpathd/0
   56 ? 00:00:00 kmpathd/1
   57 ? 00:00:00 kmpath_handlerd
   58 ? 00:00:00 ksnapd
   59 ? 00:00:00 kondemand/0
   60 ? 00:00:00 kondemand/1
   61 ? 00:00:00 kconservative/0
   62 ? 00:00:00 kconservative/1
  283 ? 00:00:00 scsi_eh_0
  284 ? 00:00:00 scsi_eh_1
  285 ? 00:00:00 scsi_eh_2
  286 ? 00:00:00 scsi_eh_3
  287 ? 00:00:00 scsi_eh_4
  288 ? 00:00:00 scsi_eh_5
  301 ? 00:00:00 usbhid_resumer
  320 ? 00:00:00 jbd2/sda7-8
  321 ? 00:00:00 ext4-dio-unwrit
  322 ? 00:00:00 ext4-dio-unwrit
  337 ? 00:00:05 plymouthd
  355 ? 00:00:00 flush-8:0
  358 ? 00:00:07 mountall
  381 ? 00:00:00 upstart-udev-br
  384 ? 00:00:00 udevd
  537 ? 00:00:00 kpsmoused
  705 ? 00:00:00 iwlagn
  706 ? 00:00:00 phy0
  719 ? 00:00:00 i915
  765 ? 00:00:00 hd-audio0
  818 ? 00:00:00 smbd
  828 ? 00:00:00 rsyslogd
  831 ? 00:00:00 sshd
  832 ? 00:00:00 dbus-daemon
  843 ? 00:00:00 smbd
  862 ? 00:00:00 gdm-binary
  863 ? 00:00:00 NetworkManager
  868 ? 00:00:00 avahi-daemon
  870 ? 00:00:00 avahi-daemon
  871 ? 00:00:00 modem-manager
  873 ? 00:00:00 console-kit-dae
  940 ? 00:00:00 gdm-simple-slav
  967 tty7 00:00:00 Xorg
  978 ? 00:00:00 udevd
  981 ? 00:00:00 udevd
  992 tty4 00:00:00 getty
 1007 ? 00:00:00 kerneloops
 1019 tty5 00:00:00 getty
 1022 ? 00:00:00 wpa_supplicant
 1026 tty2 00:00:00 getty
 1027 tty3 00:00:00 getty
 1031 tty6 00:00:00 getty
 1037 ? 00:00:00 acpid
 1038 ? 00:00:00 cron
 1039 ? 00:00:00 atd
 1085 ? 00:00:00 cupsd
 1245 tty1 00:00:00 getty
 1267 ? 00:00:00 nmbd
 1269 ? 00:00:00 plymouth
 1270 ? 00:00:00 sshd
 1370 ? 00:00:00 sshd
 1371 pts/0 00:00:00 bash
 1397 pts/0 00:00:00 ps

While ssh'ed into the machine:
$ sudo killall plymouthd
kills off plymouth and I automatically get gdm with the standard login screen. Login is succesful and the desktop comes up fine. So... my guess would be that this is indeed a plymouth issue. Unfortunately you can't just purge plymouth as it's too tightly integrated into 10.04 & simulating a purge indicates that it would remove just about everything desktop related.