I don't really think this is an issue with the fact that UDP can drop packets (I'm using Lidgren and using ReliableInOrder), but basically, in my game, the client send the input keys (if forward is prsesed, backward is pressed, etc)
Now, when lag occurs, it's not noticeable at all if the packet that says "I'm pressing forward" right now is behind schedule, because I have interpolation. However, it's really annoying when you press the space bar (jump button), and nothing happens because the packet was dropped and Lidgren needs to resend it.
How can I fix this? Please keep in mind that the server controls all position data to prevent hacking, so I can't just make jumping client-sided and send the position.