I believe this is a very strange problem, but i just switched back to PC from Mac after nearly 20 years so I'm certainly no expert with Windows 7 yet.
My new computer has a Gigabyte HD 6970 GPU connected to a Dell Ultrasharp U3011 monitor (2560 x 1600) over DisplayPort.
Whenever I have windows open on screen, which are not maximized, turning off the screen will reduce the sizes of the windows and push them to the top left corner of the screen, as seen when turning back on the monitor. Of interest, windows reduce to 1022 x 726 pixels (??) but if a non-maximized is already positioned near the top left of the screen within the bounds of 1022 x 726 the window will remain unaffected.
How can I fix this annoying problem?
[EDIT] Since posting this question i've discovered that sometimes i receive the following alert if i turn off the monitor before the computer powers down into sleep mode.