When do they happen? How often? Is there something that triggers it? Did older version of Ubuntu work fine? Maybe you could try reinstalling using ext3. Ext4 is quite new, so it could be the source of the problem.
When do they happen? How often? Is there something that triggers it? Did older version of Ubuntu work fine? Maybe you could try reinstalling using ext3. Ext4 is quite new, so it could be the source of the problem.