Those are all good suggestions. However, it could just be a sh*tty monitor
like I have.
I had a 17" Viewsonic for five years and I loved it, picture was solid as a
rock. When it blew, I got another Viewsonic, the A90f+, expecting similar
quality. The first thing I noticed was the corners of the screen quivered
like jelly when the furnace or washer was on. I took it back and got a
replacement. Same result. I bought a power conditioner, no change. The
screen shrinks and expands depending on whether the monitor is warm or cold,
it jiggles, and it's resolution dependent too. Just crappy, crappy
equipment. I wish this thing would die.
Only other suggestion for the OP is to experiment with different resolutions
and refresh rates. Some may be more stable than others.