Conversation so far:
What kind of Spirit rover equipment failures were there?
On March 13, 2006 (sol 778), the right front wheel ceased working after having covered 4.2 mi (7 km) on Mars.
What did engineers do to fix the right front wheel problem on Spirit rover?
Engineers began driving the rover backwards, dragging the dead wheel.
Were engineers able to get the dead wheel working properly again on  Spirit rover?
The right front wheel showed slight movement in a wheel-test and clearly rotated with normal resistance on three of four wheel-tests, but stalled on the fourth.
Were there other problems besides the the dead wheel with equipment wear on the Spirit rover?
Over time, the diamond in the resin grinding surface of the Rock Abrasion Tool wore down, after that the device could only be used to brush targets.
Were there problems with the spirit rover gathering data?
On January 21, 2004 (sol 17), Spirit abruptly ceased communicating with mission control.
What ultimately happened to Spirit?
After realizing what the problem was, the engineers reformatted the entire flash memory system. On February 6, the rover was restored to its original working condition, and science activities resumed.

Question: When was contact lost?
Self-contained rewrite: When was contact lost with the Spirit rover?