Windows Explorer resizes when moved

I have 2 monitors and frequently open an application and stretch it to span the 2 monitors. When I use a new instance of Windows Explorer I can span the 2 monitors, however, if I move or adjust the window, it suddenly resizes to the size of 1 monitor. The window is still sizable but is limited to the size of the single monitor. I have to set the position where I want, close it and restart it. I can then resize to span the 2 monitors again. This happens on my primary logon which is within a domain. I've tried with a local user and this problem does not appear. Any clues on how to eliminate this annoying problem? I do not have this problem if I switch to Windows XP, or with any other application.