Well, i have no way of knowing what the real problem was. For the time being after i have assembled the entire system and put it inside metal cases (that must be it) there doesn't seem to be any problem.

Could this be the end of it ?? I don't know but i will consider again all your suggestions if it ever comes up (hope it doesn't).

Yes i have tested it many times by switching the lights on and off and nothing bad happened (well my eyes didn't enjoy that much hehe).

If it comes up again the first thing to do is to re-initialize the display every minute or so just to be on the safe side. Thank god i have an RTC so no delay code is needed.

Thank you all very much.