If u ve got the same version of MCU THEN no need to flash it again.
Most important is .. when soft demands for the recovery file.. give path to that exact MCU file only.
So bfore unlocking verify that u ve got that file already on ur hdd. Else first download and then proceed.
REGARDS
ps: look at here - just posted the elaborating pic
http://forum.gsmhosting.com/vbb/showthread.php?t=194612