How old is your monitor? If it's old, that would be the problem. If it's new try degaussing it, perhaps that would help.

its a fairly new sony monitor. ive tried degaussing it, problem still persists.
the motherboard is an asus A7V333 & graphics card is G4Ti4400 . Im thinking mayb its coz i flashed the bios to a new version, could that be possible?

Yes, I think your computer is experiencing compatibility problems. But what you have, I have. My monitor flickers all the time during bootup and changing resolutions, I think it's somekind of safety trigger, since I ever got it. And my motherboard is an Asus as well. Perhaps there is nothing to worry about. I had my 17 1/2 inch monitor for atleast a year now, with nothing happening.

Yea it never used to happen before. I think i should try flashing the bios to the previous version i had before see if that makes a difference, what do u reckon?

The monitor itself is most likely at fault. What refresh rates are we talking about? What are you using to switch them? I doubt that the BIOS has anything to do with the problem, especially if it is happening at boot-time. How old is the monitor, exactly?

The monitor is just under a year old. The refresh rate i normally use is 85 Hz, everytime i go to change that or the colour depth on display properties from 16 bit to 32bit or vice versa the monitor suddenly flickers very quickly & switches itself off in an instant & when i switch it back on its ok, as i say it never used to happen at all before.

Without a doubt, you have a bad monitor. If it's less than a year old, it may still be under warranty.

Technical details (optional):

Modern cathode-ray tube (CRT) monitors use about 30,000V (30kV) to accelerate the electron beam to the screen. In order to prevent possibly-excessive X-ray emissions, the voltage is both regulated and limited -- if the high voltage exceeds a certain limit for more than a certain amount of time, the monitor shuts down for safety. When a monitor switches modes, the high-voltage supply may produce a brief "spike" of excess voltage. Since this pulse duration is shorter than the safety circuit time delay, no problem -- but if there is no time delay, or the voltage is already near the trip point, shutdown occurs. My current (older) NEC shuts down this way sometimes.

On an older monitor, this type of problem is usually caused by dried-out electrolytic capacitors due to heat build-up -- dry caps lead to no filtering, hence no delay -- or component aging. Dry caps and bad solder joints seem to account for about 75% of failures over time (for some reason NEC and Sony monitors seem to be more susceptible to dry caps than some others).

Thanks for the answer Tallcool1 , ive got it confirmed & yes it is a bad monitor, but its not under warranty. How would you go about fixing this kind of problem?

i have a similar issue with the monitor that i'm using. i realize that this started happening after my PC shut down many times during power cut. since i do not have UPS. i read all the answers here however i could not find a relevant resolution. my PC is less than a year old if u guys have any clue please let me know to fix. i shall be grateful.

regards,
affable_power