You'll need to disable PWM for PORTD pins you're using to control your LCD. See if changing
PWMCON0 = %01010100 to PWMCON0 = %01000100 helps. %01010100 turns them ALL on
for the 18F4431.

Also check your config settings. CONFIG3H has an option where you can force PWM4 output
to be on RB5 or RD5. You'll obviously want this on RB5 since you're using RD5 for your LCD.