It may be that your drive is showing signs of wear & tear, they all do at some point, oftentimes with no warning. If this is your case, at least you're getting notice.
There should be some hard drive benchmarking tools within the Ubuntu menu that will show SMART status, if possible, run the tool. Here's some additional information.
Hope that these links are of some help. Also & this will help with performance, if it hasn't been cleaned already, grab a can of compressed air & blow short blasts into the vent grooves. If possible, remove both the hard drive & optical, plus any RAM covers if present, so that the dust can escape. If the fins near the grooves are clogged with dust, the computer will run hot & performance will suffer, even if the OS is installed to a Flash drive. Eventually it'll kill it altogether if not cleaned. Note that this is a quick fix & for a really good cleaning, some removal of other components, such as the keyboard are needed. However this will serve as a test to determine if dust buildup is causing it to act up & get you off the side of the road.
Another sign of this will be that the power supply will be hotter than normal, sometimes much more so. Every time that I've performed this on a never cleaned computer (that hadn't became damaged), everything ran cooler & faster. Dust buildup is a heat insulator, which is a known destroyer of electronics of all types. Any computer tech that's worthy of bearing the title will agree on this. Yet some does a half hearted job of cleaning, especially those at retailers who performs repairs (such as GeekSquad "techs", which they self proclaim themselves as).
All computers requires internal cleaning as general maintenance at least once every 2-3 years, if in a dusty home or area, yearly. This may include the need to remove & clean the heatsink really good (hot water through the fins), clean the surface that rests on the CPU/GPU with alcohol or nail polish remover & dry fully, plus the surfaces of the CPU/GPU (gently) & reapply a good brand of thermal paste in an small amount. Less is more & temps should plunge afterwards.