Thanks for every body's help. I did download update version. I tried several methods and finally through the hints of replies from yours guys, I got it done. What I found here is a little different from each time I updated. I remember I have to back up web.config and then copy  machine key and connection stuff to release.config and rename  it web.config while rename the former web.config to different name. After that, I  was always prompt to install, which always caused the issues I posted here.  Now I did not change anything for release.config and simply unzip update files to the application. I used the original web.config. It works. So is my knowledge out of date? No more rename web.config and rename release.config?

Thanks
Hy