I'm attempting to map keyboard shortcuts in AutoCAD 2007, and I've found that no matter what I do, CTRL+SHIFT+D will always toggle DUCS when I'm in the middle of another command. I've deleted the default keyboard shortcut 'Toggle DUCS' of CTRL+D, I've set the USCDETECT variable to 0, and I've even gotten my intended shortcut (snap to perpendicular) to work when no other commands are in progress. However, the same keystroke has a different function when I'm in the middle of a _LINE command or when I'm using a grip point. I've generally been able to mold the AutoCAD interface to my preferences pretty easily, but this DUCS toggling business has been weirdly obstinate. Has anyone has this problem before?
I've been attempting to use the UNDEFINE command as you suggested, but Toggle Dynamic UCS doesn't appear to have a 'name' that is acceptable to the syntax of UNDEFINE. I've looked in the Help file for a 'name' for Toggle DUCS, but the file is thoroughly unhelpful on this point. I feel like I'm missing something basic here, but it also really looks like the UNDEFINE command is just refusing to accept any input on Toggle DUCS.