Rostock 301 heated bed problem

[Renan]

Hello,

I have a problem on the heated bed of my Rostock 301.
This printer have more than 8 months old and it was working well... now, the following problem is happening:

When I request it to heat to 110 C, the heated bed starts to heat... But, in a random moment, the heated bed shut down and stops heating.

See the following video displaying the problem.

http://renanelias.com/3d/video_problema.mp4

What I tryed:

* did the soldering again of the heated bed
* replaced the thermistor of the heated bed
* checked all wires and connectors

How to proced to solve or identify the reason of this problem?

Thank you in advance.