I started having this problem around 2 weeks ago - it's very odd.
My monitor will go into standby mode and I will wake it up, I will see the screen for about 2 seconds then it will go back into standby until I turn it off/on again. However, I found that if I move my mouse over in-between turn offs to the start menu > highlight all programs > then go back (running some sort of process I guess?) - the monitor will remain on indefinitely until its normal standby wait time.
Any ideas on what exactly is wrong with it?