My samsung monitor just turned off out of no where, but my computer seems to be still on, when i press the power button on my monitor it will turn on for 3 sec and turn back off, ive tried unplugging it and also unplugging my video card.

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

change the power supply

Unplug your monitor from the power for about 5 minutes. After 5 minutes press the power button, and then plug it in, turn it on.
If it still does not turn on, the monitor is dead and you'll need to replace it.

This could be because of the 'eco' friendliness of the monitor. Basically a lot of monitors are designed to turn off into a low power state when not in use so to preserve power and life of the monitor. I would return the monitor as the sensors that control this seem to be broken in your monitor.

I have the same exact problem. The monitor seemed fine yesterday. Today, the power button light just flashes on and off, with nothing on the display.

Please try again to turn the monitor off. Hold down the Menu button while the monitor is turned off, then press the Power button again to turn the monitor back on. This should unlock your OSD menu. regards

check in back side of monitor reattch power cable after clean dust from it.
also check with other power cable that your monitor turn on with other cable.

I didn't have the monitor connected to the computer, and that's why the power button was unresponsive. After connecting it, the solution above worked for me.(My KVM switch was set to a computer that was turned off)

• OSD Lock Function: To lock the OSD, press and hold the Left button while the monitor is off and then press power button to turn the monitor on. To un-lock the OSD - press and hold the Left button while the monitor is off and then press power button to turn the monitor on.
  

Known issue -- can get a replacement if still under warranty. The planar rma techs are really really nice.