Can anybody offer any suggestions here. Each time I open a second or third file in CorelDraw x5, the windows seem to lose the top MIN, Max Close icons. You know the ones that sit at the top right of each window. Because of this I'm unable to close or edit the work. In fact NOTHING works. I'm running Windows 7 64 bit with a TON of memory.
George is probably right that you've accidentally changed a setting. I run X5 with multiple files open all the time under Win7 X64, and I've never seen the behavior you describe.
But on occasion I've clicked on the wrong thing and changed the workspace without meaning to. If you've saved your workspace, you can reload it and see if that doesn't fix it.