Can you be more specific with your setup? Is this an issue you are having with an H90? Are you using the latest H90 software?
What device are you using to send PC messages? Is it only sending a PC message or is it sending other MIDI data at the same time? You may need to use a MIDI monitor to see exactly what is being sent. The PC should happen immediately on the H90 and the display should also change immediately to reflect the new Program.