I actually started out trying to burst a number of AEC objects we received from a client (without answering the question of WHY we want to burst AEC objects,) but couldn't select the proxies as we have been able to do in the past. Finally, I decided there might be something wrong with the file, so I tried auditing it. I get a message stating that "eWasOpenForWrite" along with an error message for (apparently) each element stating: "Could not instantiate AecDict!" Any suggestions what is wrong here? Google searches didn't turn up anything useful, other than to check our AutoCad installation in order to verify the paths are correct. I'm sure all is fine with paths, as this is the only file on which we've had this problem. Thanks, in advance, for any help or suggestions.