Suddenly, the name of various lists like Announcements, Suggestions etc. on my Homepage has changed to Untitled , Untitled  and so on...
How could this happen?
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If someone has added new instances of a list without naming it, the name of Untitled is provided and SharePoint adds the instance number (, , ...) to avoid duplicate names. This is often the result of someone accidentally hiding a web part (e.g. a calendar view) and then adding a new instance of it to the page rather than unhiding the existing one. What happens is that folks will use the icon to "Close" (or hide) and then they don't know how to get it back. To verify, edit the page so that the "add web part" links appear. When you are looking at the web part gallery, take the option to display hidden web parts. Make the hidden web parts visible again and then delete (not close or hide) the copies.
This may not be what you're seeing at all, but it is very similar to something I saw once at a client and this was the remedy.
Found simple Solution -- Very close to what Rob suggested!! Open Web Part Maintenance page and DELETE the web parts which are not open or those which are showing errors. That's it!
Reach Web Part Maintenance page by adding '?contents=1' extension to URL of homepage of any department .