A couple of weeks ago, the Hubble Telescope suffered from a serious hardware malfunction in the data handling circuitry. A remote repair is now planned with the hopes that some of the telescopes 18 year old redundant circuitry can be utilized.
A trip by the space shuttle Atlantis to add new instruments has been delayed due to the problem and will need to be rescheduled.
The Hubble is the most famous of all deep space telescopes due to the controversial cost and a history of problems. Overall though, it is hard to argue with the vast knowledge that has been gleaned from Hubble data. Many serious questions have been answered and new mysteries have resulted but most memorable to me are the wonderful images that have been captured (once the flawed mirror was replaced during the first service mission.)