I had a similar issue. RSD Lite (https sites google com [slash] site [slash] motosbf [slash] rsdlite) is your first port of call, using the appropriate image from http sbf droid-developers org [slash] smi [slash] list.php .
However, that only partially worked for me. It failed first on the logo - so I extracted the zip from droid-devlopers, and edited the XML to remove the complete line <step operation="flash" partition="motoboot" filename="motoboot" ...
After that it would flash up to and including the radio, but then fail on the system_signed ( as it's over 100MB).
To get around that I used the enhanced fastboot from mattlgrof's package http forum xda-developers com [slash] showthread.php?t=1936512, and manually compted the final steps in the xml file in the extracted zip folder:
fastboot flash system system_signed
fastboot flash cdrom cdrom_signed
fastboot oem fb_mode_clear
Then a
fastboot reboot
And all was well - back to stock. Upgraded from there, and flashed CWM and then rooted. Hope this helps