This question of mine is similar to this question.

Unlike the problems faced by the user who asked that question.. I am not facing any problems anywhere. Infact my installation process was flaw-less unlike the one in the question.

It's just that whenever i login for the first time after a reboot, i get the same dialog-box as in that question.
There are infact even more similar questions on the main site but none of the answers addressed that how to reach the the problem causing area and analyse it so that it could be repaired then on.

I want to know that what's causing that error message which shows up only when i log it after a reboot (not with subsequent logout-login)

Additional info : its a ubuntu minimal install - added LAMP & Mail server stack via tasksel - cinnamon as GUI - MDM as LoginManager