Gateway FHD2400 HD Display for my Mac Book

If you trash the preferences files associated with displays, you will get a fresh start again with the Gateway. Here are instructions for how to trash the preferences...

What you want to do is trash all files with windowserver in its name and ending with plist. The path to one such file, starting by double-clicking on the hard disk icon would be /Library/Preferences where you should see com.apple.windowserver.plist. Throw it in the trash. Again starting from the hard disk icon, find /Users/accountname/Library/Preferences/ByHost and you should see a file com.apple.windowserver.xxxxxxxxx.plist where xxxxxxx is a string of numbers and letters and accountname is the name of your main user account. If you have multiple users on your Mac, you might also want to trash the same .plist file under all the other accounts as well.

Once you have trashed the above files, restart the Mac. When OS X restarts and finds those files missing from their expected location, it will create fresh copies with factory default values. That will give a fresh start to any attached display. Hopefully that will clear up the problem. Good luck.