I have the same problem after using Data Connect to add a polyline shapefile to my drawing.
I would roll off the Data Connect Diloag an onto the shapefile...HANG...CRASH.
Thanks to Alfred's suggestion I checked ROLLOVERTIPS and SELECTIONPREVIEW.
ROLLOVERTIPS was set to 0 already, SELECTIONPREVIEW was set to 3, I changed it to 0.
Everything works good now.
I checked these two settings in Civil3D 2011, where I have no problems with shapefiles, and ROLLOVERTIPS was set to 0; SELECTIONPREVIEW was set to 3. Those same settings will not work in Civil 3D 2012.