Why isn't this working

[Kp]

0x66, SID_FRIENDUPDATE
They don't have 0x066 so I'm not sure if they're the same thing

Yes.  As in math, leading zeroes may be safely ignored/discarded (except when they specify octal). 0x66 = 0x066 = 0x00000066.  Why anyone would write 0x066 is beyond me though - either write it shortest or write it in the last of the three forms if it's a dword and you want to be explicit about that.

[Fr0z3N]

* Fr0z3N hates math