OK, here is my story of finding the best solution. First of all, if you want to skip my story and if you want to resolve this issue quickly, try this link at Apple Discussion Forum,
http: //discussions.apple.com/thread.jspa?threadID=2659385
(I am not allowed to post link yet, so I put in other format. I added a space in between so you need to retype the whole link.)
Basically, all you need to do is as the following,
"Reset iPad settings. From the Home screen choose Settings > General > Reset > Reset All Settings. All your preferences are reset, but your data and media aren’t deleted."
Now, here are my findings after struggling with this issue these two days.
1. reset with pressing the home button and power button would not resolve this problem.
2. restore to previous backup set would not resolve this problem, either. I guess it is because some conflictions between apps. But don't know what they are.
3. restore to "as a new iPad" can bring the Maps back but you will lose the data, like diary and notes.
4. if you back up the data of your diary, notes, etc, the backup data set cannot be restored to your "new" iPad. I guess the restore system treats your iPad as another "new" device and the restore process will not be successful. You still lose the data.
5. Fortunately, the Apple Discussion Forum provides the easiest and safest solution. There is another "reset" way through General setup page. It is easy and safe. The data is not losing. And the beautiful part is your Bookmarks in Maps are still kept. The only things impacted is your wallpaper and wifi link which is easy to get it back within only a few seconds.
by the way, it appears that not too many people encounter this problem. The reason I put this link to this forum is because if you type the key words "Maps shut down", "Maps not working" in Google, the serach engine will bring you here. So I put the link and solution here. You dont have to restore. All you need to do is go to setting page and reset. And say hello to your Maps again.