I supplied a few of these 12-14 months ago and I have today had my second one so far this year fail. Having searched around it seems they are [Only registered and activated users can see links. ]so backup your data asap and consider replacing with a Samsung 840 or Crucial MX100 whilst they are available for £50-60.
One model was the 60GB and one was the 120GB so looks like they will all be affected, this particular one is SDSSDH-120G-G25 manufactured 3rd April 2012. They have 3 years warranty and Sandisk should upgrade you to the Ultra Plus.