The last week or so I have noticed an odd thing. When I turn on my monitor, my browser windows are all half the size they were when I turned it off. Sometimes when I turn it on the taskbar is even half way up the screen for a few moments, as if turning the monitor on and off was forcing it to change the resolution. I use firefox, running windows 7.
I suggest you may try this freeware (Autosizer) to force the size of any open program : http://www.southbaypc.com/autosizer/ Hope this help ;)