I forced shutdown my system a fateful evening and didn't bother booting it until early the next morning.
When I did, I noticed the booting process was taking too much time at the splash screen so I decided to check up what was going on, a quick press on the f2 button gave me a more detailed view of the booting process on terminal, it showed that my dear jenny had filesystem errors, displayed the error "mountall: fsck / terminated with status 4" and politely asked me to run fsck manually on my linux partition.
I knew which of the partitions held my linux OS in this case, it was the /dev/sda5 so I simply forced shutdown and rebooted again, selected the "Advanced boot options for ubuntu" then booted into the recovery mode, this gave me a list of options of which I picked the "root" option which gave me access to the root terminal after entering my root password.
Once in the root terminal, I ran "sudo fdisk -l" [enter], did this just to be sure of which partition I had to deal with, in this case, as mentioned earlier is the /dev/sda5 yours might be different, just check the last column of the listed partitions and you should know which one to deal with, the next command was just a simple "sudo fsck -f -y /dev/sda5" [enter] (the -f flag would trigger a force-check regardless of the state of the disk and the -y would ensure that you don't have to keep pressing the "Y" [yes] key to respond to the processes 'questions'). After running that (it might take awhile to complete),
I simply rebooted by typing "sudo shutdown -r now" [enter] and voila!!!, my jenny was up and running again. I'd iterate the commands below so we can have some closure. ;) after each line of command, the [enter] key is tapped with fervour (this invokes the linux genies into performing their magic)
sudo fdisk -l
sudo fsck -f -y /dev/sda5
sudo shutdown -r now
[enter] simply means a hard or soft tap on the enter key. ;)
Hope this helps.