Hi rachael101,
I would suggest you to try the steps below and check if it helps.
Step 1: Change the refresh rate.
http://windows.microsoft.com/en-US/windows7/Correct-monitor-flicker-refresh-rate
Step 2: Yank your power cable from the
monitor. Turn it on with power cable off. Plug it back in and turn on monitor.
Step 3: Try a factory reset from the
monitor menu.
a)
Click on the monitor menu, scroll down and go to factory settings.
b)
Scroll down and select all settings to reset.