I turned monitor off and now it won't come back on

Most likely the power board is defective. A new power board will cost $40 to $100 depending on your model. ShopJimmy.com is a good place to look for boards. They are not too difficult to replace if you have a minimum of electronic repair experience.

If it doesn't turn off by holding the power button down for 10 seconds, then it cannot be turned off by the power button alone, like most modern lcd monitors. Most modern monitors goes into standby mode. To completely cut power, you must unplug the power cable.
I've enclosed a link to the install manual for reference.
Samsung SyncMaster P2050 User Manual Page 7

Make sure the VGA cable is properly inserted to your pc and monitor

Try turning the power off, press down the contrast and britness setting bottons and turn the monitor back on and release the buttons.

Next if that dosent work try holding the menu button down until you get osd unlocked come up.

Hope this helps.

that blue light show and error or faulty problem internally or there a problem with in the connection or computer but first check the makers website or manual for troubleshooting.

Yea I fixed it ..bought a new monitor......I tried the old monitor on two other PC's same problem.....

moniotr switches into power save mode when it is connected to the computer and there is no signal for the computer. Try following the steps below which i recomended for another poster as well

Unplug the monitor from the power
Unplug the monitor from the computer
Plug the monitor back in.
Try turning it on.

DOES IT SAY "NO SOUCRE DETECTED" or soemthing like that???

if it DOESN'T it means there is something wrong with the computer.

if it DOES:

plug it back on to the computer, turn the computer power off.
Press and hold the power button on the computer for about 15 seconds.
Plug the computer back on.
Try turning the computer on.
if it's not turning on again there a problem either with your monitor cable, or the plug, or the video card plug. It is unlikely that your video card is broken if you hear no wired series of short and long beeps when you try turning the computer on.
Good luck.
Give us updates if you need more assistance

I have the same problem and I think its the circuit board on the power on button and blue led. I unplug the board when the monitor is on and then the monitor stays on and works OK.
It don't make any sence it is only 3 parts switch led connector
anybody else run into the problem

I just had this problem at work and what I did was I powered up the computer and went into the menu. I went to the 2nd to last button and selected the reset. It's working perfectly now. I do not know if it will last but it's easy and free.

Do you mean the computer is sutting down but on the monitor showes different colors if so you might have a problem in the system you might have to reinstall you OS if the computer does shut down but the monitor stays on and flashes different colors you have to shut the monitor down manually with the power button on the monitor.