Power Adapter acting funny!

My power adapter is acting completly funny. Last night it was working perfectly. This morning I tried charging and it didnt work. At first I thought it was the power outlet in my class. After my class i went to a computer lab and tried it again. Same result!! didnt work. The green light flashes for like 2 secs at first and stops flashing. Later i borrowed a charger from my firend and tried it on my computer. It worked.

Just to give it a try, i tried charging his computer with my charger(the broken one) and that worked too. That was really weird. I came back home and tried in my cousin's mac which didnt work!

How can that happen???