Conversation so far:
Did something go wrong with communicating with the rover?
As of 2016, there has been no communication with the rover since Sol 2210 (March 22, 2010).
Did something happen to make the rover not communicate?
It is likely that Spirit experienced a low-power fault and had turned off all sub-systems.
How many times did they try to communicate with it?
Each sol, the Deep Space Network mission controllers sent a set of X-band "Sweep & Beep" commands.
Did they give up on the rover?
But even with this new strategy, there was no response from the rover.
What was the last thing the rover communicated?
Due to the possible clock fault, the timing of these 20-minute listening intervals was not known, so multiple "Sweep & Beep" commands were sent.
Did the rover send any important information?
If the rover heard one of these commands, it would have responded with an X-band beep signal, updating the mission controllers on its status.
Was there any other factors that contributed to the communication failure?
It is also possible that the rover had experienced a mission clock fault.

Question: Why would the mission clock fail?
Self-contained rewrite: Why would the mission clock fail on the spirit rover?