Very slow boot due to mounting filesytem

I saw some problems with the same a year or so back.

Do you have a file named/var/lib/ureadahead/pack?

If so, delete it with sudo rm /var/lib/ureadahead/pack and then do a reboot (this will force a rebuild of the pack file used by ureadahead).

After a couple of reboots some have reported to work and some claim the problem came back.

If the latter remove and (re)install ureadahead. You can do that from USC:

Resolving these sort of issues can be more trial and error. From the look of your trace there is a probably interrupt issue which its hanging on.

So here are a few things to try.

1. Open you BIOS settings. Try disabling legacy USB Support
2. Try some one of the common boot options - "nomodeset", "noapic", "nolapic" or "acpi=off" as per this AU question and answer.
3. UReadAhead issues - see Rinzwind answer above (you beat me Rinzwind!)
4. Try disconnecting all devices - make sure you limit yourself to having a wired keyboard and mouse plugged in.

You also mentioned that /dev/sda5 was mounting several times. It might be useful to check that your /etc/fstab file looks ok and that you dont have any cross-mounts. See mine for an example (n.b. dont copy mine - just see if its as simple as mine)

more /etc/fstab

# /etc/fstab: static file system information.
#
# Use 'blkid -o value -s UUID' to print the universally unique identifier
# for a device; this may be used with UUID= as a more robust way to name
# devices that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    nodev,noexec,nosuid 0       0
# / was on /dev/sda5 during installation
# Commented out by Dropbox
# UUID=80ff19ee-34d0-484a-9f0d-57ae5fff6caa /               ext4    errors=remount-ro 0       1
# swap was on /dev/sda6 during installation
UUID=b309d064-5360-462e-86ff-b380a38bb56a none            swap    sw              0       0
UUID=80ff19ee-34d0-484a-9f0d-57ae5fff6caa / ext4 errors=remount-ro,user_xattr 0 1

... and confirm that /dev/sda5 isnt cross mounted i.e.

mount
/dev/sda5 on / type ext4 (rw,errors=remount-ro,user_xattr,commit=600)
proc on /proc type proc (rw,noexec,nosuid,nodev)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
gvfs-fuse-daemon on /home/dad/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=dad)

Its also worth forcing a filesystem check on reboot

sudo touch /forcefsck