Same problem already happened once so I rolled back to the latest non-problematic version, but it's been months now and I thought to try gain. Still the same problem, so now I thought to ask for help rather than rollback to this, now very old, version.
Currently I use 266.58 version drivers for Windows 7 x64 and GeForce GTX 275. (Downloaded from the nvidia website) I have two monitors, Samsung SyncMaster 223BW (LCD) is primary and LG F900B (CRT, old but still works) is secondary.
The problem: when I turn off the monitors (both or just secondary) all of the windows that were on the secondary monitor get moved to the primary. This also occurs when I use Sleep. Again, in the old drivers this didnt happen, but now it does and is very annoying, requiring me to manually move the windows back to the secondary monitor (which I use for most of the windows).
I had no luck searching for this on google, but maybe somebody here will have a useful suggestion.