I couldn't get Z4root to work eather but eventually i found an app called gingerbreak and it worked perfect for my optimus m just fallow the instructions
Unfortunatly about a day into having my rooted optimus m i decided to mess with it and used rom manager to back up the existing rom and install an new one (didn't really know what i was doing) i'm kinda a noob to android devices. anyways when i turn on the phone the lg logo apeers then it goes to the fast boot screan and sais
fastboot mode started
udc_start()
i don't know what to do and i haven't been able to get it to start in any other mode exept if i hold vol_up + back + power and hold them until the four main buttons light up it gets stuck on the lg power up screen. i tried downloading the kdz updater but for some reason it wont let me run the .exe file
please help with this