Close button not closing anymore (Cad 9.0)

Hello: I have autocad mechanical 9.0, and all of a sudden, the close button isn't working. I open a drawing, and try to close the little "X" on the upper right side (see pic) and it does nothing. I have to close cad in order to close out the drawing.

any ideas? i tried it on multiple drawings...and it's always the same.

thanks,

Proctor

Have you tried to run a repair from the AutoCAD disc? There may be a missing link in the software that this repair may fix.

are you in SDI mode?

set SDI=0 and see if that works.

dbroada: SDI command worked!!! It was set to 1.

thanks so much for your help!!!!

Proctor