When using AutoCAD functions that open a Window's Dialog Box, such as the "Attach" or the "SaveAs", a setting maybe changed where instead of the box appearing, the user is prompted in the Command Line to type where they want it. To return AutoCAD to it's original setting where it opens the Dialog Box, follow these steps.
1) Type the command "FILEDIA" into the command line
2) It will prompt you with "enter new value for FILEDIA < 0 >:"
3) Type 1 and press enter to get the Dialog Boxes. (Type 0 for no Dialog Box)
There you go. Should be fixed. Have fun!