From what you seem to have posted such as:
computer freezes often for no apparent reason and has to be rebooted
upon reboot, message appears saying "errors were found when checking disk drive for '/'"
documents will not open in libreoffice
These make me think that for some reason or other you hard drive is being unmounted from time to time while you're using Ubuntu, it could be a hardware issue such as a faulty connection to your Hard-Drive, however seeing as you also have a:
- message appears saying that Ubuntu has experienced an internal error, but 'report a problem' program always crashes before completion
I'd assume it's more of a software issue, so if I were you I'd back up all of your files in your Ubuntu partition on an external hard drive and reinstall Ubuntu in the same place. A fresh install does the job 99% of the time unless its a hardware issue with your netbook.
Also as a precautionary measure, whenever I mess around with Operating Systems and Booting related things I always make a full back-up of all my partitions, might be over the top and I've only every had a "losing all my files on a partition" problem once, but when I did have it, I was pretty glad I'd been backing up my files as all I had to do was recopy them into the freshly installed Ubuntu OS.
So bottom line, its good practice to back-up regularly (especially if you have bugs with your OS not being able to read files and more worryingly errors concerning the root "/") and even moreso if you're installing an OS. But I'd reinstall if I were in your situation, seeing as those bugs could be so many different things and finding a solution to all of them separately could take you a while.