Looks like general system flakiness to me -- RAM or motherboard. Basically, something is corrupting your filesystem meta-data. It is unclear whether the corruption is occurring in RAM (with the bad meta-data eventually getting flushed back to disk), or if the corruption is occurring during disk I/O.
I seriously doubt it is a kernel/driver bug, but I suppose anything is possible. Did you by chance update to a newer kernel around the time the corruptions started? Did you install any third-party device drivers (i.e. ones that didn't come from the Ubuntu repository)?