Be sure to set HS in config word. This forces the PIC oscillator drive output
to a higher level required to drive the high-speed oscillator.

The default config word osc setting in 18F4550.INC header file is for XT.

Look in your PBP directory for 18F4550.INC, and change XT to HS, or change
XT to HS with your programmer software before programming the part.