Malfunction after “upgrade”

Hi. Got the message of upgrading Shiled to latest. Clicked “uograde” and the page hung. Checked back after 30 min, nothing happened. I had to do the “forceoff” thing. When reentering tha adin page Shield is no longer there. Downloaded it once again but it will not install. Says the “target folder” (or something like that translated) already exists. Any idea on how to move forward?
ps. The same thing happened a few days ago when trying to upgrade Shield. I deleted all content and used dulicator to reinstall. It worked until now when trying to ugrade again.
Thanks… k