So, hardware trouble caused a VPS to go down. This VPS was running a MySQL server in a slave setup. Not surprisingly, the unclean shutdown broke succesful slaving.

There are several possible causes for the slave setup breakage. This time it was the local relay log file (mysqld-relay-bin.xxxx) that was out of sync.

SHOW SLAVE STATUS\G looked like this:

...
       Master_Log_File: mysql-bin.001814  <-- remote/master file (IO thread)
   Read_Master_Log_Pos: 33453535          <-- remote/master pos  (IO thread)
        Relay_Log_File: mysqld-relay-bin.001383  <-- local/slave file (SQL thread)
         Relay_Log_Pos: 34918332                 <-- local/slave pos  (SQL thread)
 Relay_Master_Log_File: mysql-bin.001812  <-- remote/master file (SQL thread)
...
            Last_Errno ...