After reading post some guys been having probs flashing pic18f2550/4550/2455/4455
using a willem 4.5 icsp.
if you brought your willem from sivava the chances are MCLR/Vpp icsp pin header is dead, after stressful few hours trying to get the pic ID i found the above fault i ran a link from Vpp point beside the row of dip switches to pin 1 of the pic (success) ..tools, winpic800, willem 4.5 programmer.

ISCP PIC

Vpp - 1
Vcc - 20
Gnd - 8/19
RB7 - 28
RB8 - 27

These pins are for the following pics ..PIC18F2550/PIC18F4550/PIC18F2455/PIC18F4455.