I finally got back into playing Deus Ex last night and I thought I had completed every quest, searched out every powerbar and hacked every single office, computer and hidden safe in Detroit. So when I went to get on the copter, a quickly clicked on accept, when I saw the word "Warning", but it was too late. After looking it up on the net, it appears the warning probably read "Warning there is an Unfinished Side Quest". I wish I could have gone back and done it.

Anyhow, Hung Hua is a pretty facilitating city and I am having fun exploring there and doing side quests for Mei. I still haven't found the hive.

It brings up the message even if you did all the sidequests in the area. Don't worry, you probably didn't miss anything.