How big is the file and does it contain a lot of text? I know when I used to bring CAD files into ArcMap, the amount of text in the CAD file dramatically affected the load time (which may seem like ArcMap is hung). By removing the text, I was able to greatly decrease the time ArcMap took to process the CAD file. A few pieces of text should not cause any problems but having hundreds of text elements in the CAD did. It was a very exponential curve.
Also I notice that sometimes CAD files will have huge extents since there may be a couple elements far away (often near the origin) from the main body of the drawing. ArcMap seems to slow down when the spatial extents are that big.