Unable to open mail /accounts in N9
 

I am unable to open the Mail application on my N9. The application simply does not launch.
Tapping the application icon causes the icon to blink, like all the other icons, but there is no other response.
All the other system apps (messages, phone) work fine.

I have been using Mail on the N9 for more than a year now without any such issue, and I haven't changed any settings recently.

Any help would be appreciated..

(I am using version PR1.3)

Edit:
Further, none of the items (i.e. Installations, Calendar, Contacts, Mail, etc.) in the Settings > Applications menu opens either.

Re: Unable to open mail /accounts in N9
 

Update:
So i reset the phone, using the
Settings > Reset > Restore settings menu,
and after re-inputting the settings, the Mail app started to work again.
However, it got stuck mid-way through downloading the emails from the configured account, and asked "Mail not responding? Close/ Wait."
After I closed it, the earlier issues of not being able to open the app, or certain menu items in settings, have returned.

Any idea what could be wrong?