If the respective dwg doesn't have AS objects, you can do the following :
- start AutoCAD alone.
- set the system variable "demandload" to value 2. This will not allow AS to load, when you open the respective dwg.
- copy/paste the whole dwg contents (you can select it with "Ctrl+A") to a new dwg, created with AutoCAD. Save that dwg.
- set "demandload" back to 3, and close AutoCAD.
- open AS 2012 and then open the dwg.
Make sure before you copy the contents of the dwg to the new one to not have any objects in it that have a name that starts with "AST". You can check the objects inside the dwg by using the CAD command : Quick Select.