Try another hdmi cable. You can get inexpensive cables at Amazon.Try the monitor on another computer. 

juanmb,

Using video card HDMI to ST2320L HDMI, boot the operating system into Safemode. Do you see the red dot lines?

If yes, get the monitor replaced.
If no, then the culprit is either the video card or the video card driver.

Do you know how can I select the monitor as the output in safe mode? (it's a laptop) I have windows 7.

Hi, I've just bought a new (high quality 1.4) cable and it's the same thing (I tried 3 cables). I can't not test the monitor with another computer since i dont have another one with hdmi. I did test it with another operating system on the same computer though (windows and ubuntu) and its all the same. And like I said before, If I connect the computer to a Bravia TV, It looks great. I'm uploading some pictures right now. thanks.

http://imgur.com/a/cJTEs

That brings up a whole different set of problems. We were not aware that the monitor was being used as a secondary to a laptop primary. In the laptop Display Controls, is the secondary ST2320L resolution set to 1920x1080 60hz?

What specific laptop? What specific laptop GPU?

yes, it's always been.

Its a VAIO VPCEB13EL.. I believe the GPU is integrated in the Core I3. . in the properties it says Intel GMA HD Video BIOS 1930.0. I've always used it as a primary monitor (laptop screen always turned off) for 2 years. thanks

Ok. I think the laptop video guys need to get involved with this. For now, moving the thread to the Laptop Video board to see what they think.

Could anyone from dell give me that number I need to call tech support? my monitor only has these numbers which dont work on the site:

S/N: CN-0DFF58-72872-0CM-0KGL

REV A01

DEC 2010

4000817

thanks