I've found that if I have a .Net command that calls acedCmd/acedCommand, etc, within it, and the defined command is itself executed within acad.lsp at startup, the AEC tab on Design Center does not work. Any drag operations (however slight) quits the drag operation immediately with a "bong" system sound. If I run the command that used acedCmd manually, instead of at startup, everything works fine. Is calling acedCmd during ACAD startup causing a component not to load somehow? It doesn't matter what command acedCmd executes, just that it does. By the way, I've removed everything from acad.lsp execpt the call to my command. Any insight appreciated.