Shake his hand and say "Nice to meet you again. How have you been doing?" for the following reasons.

1. The reasons you both had problems were professionalism related and not personal issues. It would be a nice gesture from your end.
2. Always give a chance, when you are in doubt. He would have changed professionally learn a lot during this five years.
3. Be the first person to build the bridge. It gives you an opportunity to understand the individual and influence. Being courteous is a part of being professional.

It is good to be nice to people and treat them how you would like to be treated.

Shake his hand and say "Nice to meet you again. How have you been doing?" for the following reasons.

1. The reasons you both had problems were professionalism related and not personal issues. It would be a nice gesture from your end.
2. Always give a chance, when you are in doubt. He would have changed professionally by learning a lot during these five years.
3. Be the first person to build the bridge. It gives you an opportunity to understand the individual and influence. Being courteous is a part of being professional.

It is good to be nice to people and treat them how you would like to be treated.