Hi AZFL,
In my opinion it is very rare that monitor flickers are normally caused by voltage variations because the variations would need to be very large for this. Usually all AC devices are rated for a good range (typically 180-240V). So there are some possibilities I see -
1) There is some problem in the monitor not related to the supply - get it checked.
2) If indeed it is a voltage problem you suspect - it could be a problem because of varying mains supply (which you can easily find because any other bulb in your home would also flicker)
Otherwise it could specifically be a problem of your UPS output which you can also check with an AC mutimeter or another bulb.
The easiest way i would say is to take your monitor to your friends house and try connecting to his PC to check if its a specific problem in your house.
Hope this helps !!!
Karthik
