MacBook Pro :: Freezing Up And Not Allowing To Click On Any Item

I had to force shut down my MacBook Pro today as it was freezing up and not allowing me to really click on anything.  All it let me do was close out of Photoshop.  What happened was FireFox decided to crash and not reopen after attempting to install an updated version of Flash Player.  When I rebooted after the force-shut down (holding down the power button to turn off my computer, which has always been effective in the past), I got a screen for OS X Utilities with the following prompts: 

Restore From Time Machine Backup

Reinstall OS X
Get Support Online
Disk Utility 

So, the first one is out of the question.  In the 5 1/2 years I've proudly owned my computer, I have never created a Time Machine account/backup.  I have preferred to use an external hard drive.  Unfortunately, the other prompts would be A-okay, if it weren't for the fact that I've been lax in updating my backup and haven't backed up to my external in about 8 months. 

Unfortunately, to Reinstall OS X, my computer wants to erase all my data, so I need the backup of my files.  (I have a lot of photos on my drive).  But it says I can't even reinstall, because the hard drive is locked..And it won't repair my hard drive.  The prompts for why it should be repaired are: Invalid content in journal, Invalid B-tree node size, The volume could not be verified completely. 

When I try to create a new image to backup to my external in order to wipe my system, it says "Unable to create "disk0s2.dmg" (invalid argument).  Now, I am not totally computer illiterate.  I can follow a set of instructions and do my own IT work basically 99% of the time. I don't want to loose my images or lesson plans (I actually just got my school issued laptop and was going to transfer school files over to my school-issued computer as soon as I finished with my Internet needs (bills)). 

Info:
MacBook Pro, Mac OS X (10.5.8)