Fixing thunderbird configuration could not be verified gmail

For past couple of days I have been trying to configure Thunderbird to access my mails from new gmail account  in office and it was reporting me "configuration could not be verified gmail" I was troubled because I was using Thunderbird for quite a long time without any problem.

Fix error in man-db in Ubuntu

yesterday while loging on to mysql found that my password was not working and after googling to resolve the problem I was able to fix the problem but encountered another error message when I was trying to reconfigure dpkg
i issued the following command 
sudo dpkg --configure -a
Setting up man-db (2.6.3-3) ...
Can't exec "/var/lib/dpkg/info/man-db.config": Permission denied at /usr/share/perl/5.14/IPC/Open3.pm line 186.
open2: exec of /var/lib/dpkg/info/man-db.config configure 2.6.3-3 failed at /usr/share/perl5/Debconf/ConfModule.pm line 59
dpkg: error processing man-db (--configure):
 subprocess installed post-installation script returned error exit status 13
Errors were encountered while processing:
 man-db