Unity freeze when sub window opened (i.e. Build settings, color picker, etc)

When I attempt to open any sub windows, like the build settings, or color selector for lighting, as well as when I try to re-size the editor window, Unity will freeze up, not allowing me to move the window or use any of the interface. I have to end the application from task manager, as it seems to be unrecoverable. If it's needed I can provide system specs if it helps for diagnosis, however I have never encountered any similar difficulties with any other program. I was hoping someone might know what the problem is, or at least a workaround for it. Thanks much.

Note: Running the free version (4.3.4) on Windows 7 Ultimate (64-bit)