for some strange reason, when i bouht my p690 (optimus net), when i tried to boot in recovery mode, the phone factory reseted, without first asking me if i want to...
i thought that it was other combo for the buttons to log in recovery but i was very wrong...
the phone (at least mine) had no recovery, just had factory reset on the vol up, home and power buttons combo...
i flashed cwm recovery with the help of adb (java software for pc) and it works like a charm....
you can read all about this in the thread "all root ... something..."
hope you manage to make yours work...
good luck!