Short answer for Google Users: Hold "Auto" and "Menu" while turning the LCD on to get additional options in the OSD. These options should allow you to correct the issue.
About 6 months ago my Acer AL1916 LCD monitor started to display all images too brightly. I couldn't work out why the Acer displayed at the correct brightness and when I hit the auto button it would also display at the correct brightness for a second before reverting to an unusable brightness that hurt your eyes. I stashed the monitor away knowing that I had a long 3 year warranty and would get it repaired when I was ready.
This afternoon, for some reason, I decided to try it again. Still dumbfounded as to why it could display images correctly for a second but not permanently I decided to do some research.
I Googled this, Googled that, and finally found a service manual. The manual was mostly full of useless information, but one little piece of information got me thinking. I tried turning the monitor on while holding the auto and menu buttons. The LCD turned on and the on light stayed orange. I knew I was onto something. I opened up the OSD and started fiddling. I noticed that some menus had more options than what was previously listed. I found a couple of factory reset options under "Exit" on the OSD and they fixed the brightness issue.
What a pain in the butt! Anyways I am now using my LCD again and I'm much happier.