I am flashing a radio to an MyTouch 1.2 and I get this:
C:\AndroidSDK\tools>fastboot flash radio radio.img
sending 'radio' (21504 KB)... OKAY
writing 'radio'... INFOsignature checking...
FAILED (remote: signature verify fail)
C:\AndroidSDK\tools>fastboot flash radio radio.img
sending 'radio' (21504 KB)... OKAY
writing 'radio'... INFOsignature checking...
FAILED (remote: signature verify fail)