Dell U2410 screen lost signal in DVI, HDMI, VGA (black flashing screen at random times)

Hi, I have the monitor model Rev 02, u2410, replaced unit from tech-service and still have the same problem like with first one. The entire screen will intermittently flicker to a complete black and back again. Sometimes flashing once other times flashing multiple times at random times. I use PC (ATI Radeon, windows 7 64 bit) so I thought that 59 Hz refresh rate in Windows 7 and 60 Hz refresh rate in ATI is the problem. I forced ATI to 59 Hz by refresh lock and still got flickering. I also changed resolution to 1280x.... with 60 Hz but problem persist. I've checked cabling by connecting two laptops (ATI Radeon, Windows 7) by HDMI and VGA, and Apple Mac Mini by VGA but problem still persist. Funny thing is, that I took first unit to my work, and our IT Specialist connected laptop by VGA to it and there was no problem with black flickering. The difference was: - much more stable desk, I think when I use it at home, screen is shaking little bit by desk, when I write on keyboard for example, - better electric infrastructure, - monitor spent whole night packed packed into bubble foil very close, so if any mechanical part of display became unglued, it spent whole night sticked. - we connected VGA cable and move display not so much as I have to do it at home to connect cables That displays are refrubrished - is it possible that I got 2 units with same problem unsolved? For example with Power Supply or with the inverter? or maybe something in screen became unglued and not connecting well? Additional Info: I tried turning off the laptop with the monitor on. With that i can only play with the OSD using touch. anyway i noticed that even without the laptop, the monitor was still blinking. i can play with the OSD even when it blinks. I have a mouse and keyboard attached to the 2 USB ports at the back, and when the monitor turns black, i can still type and move my mouse. Any suggestions? Another replacement? Thanks In Advance for any suggestions