If you are running into a problem with importing a CAD file try the following steps:
1. Download this tool http://usa.autodesk.com/adsk/servlet/index?id=6703438&siteID=123112 (195 Meg)
2. Open the file using DWG TrueView
3. Check to see if the units of measurement match the actual measurement. We have seen UOM=feet and the actual measurements are in inches & usually happens on remodels.
4. Check to see if the CAD file has multiple views stored in the same file (see this example, below)
5. Check to see if the CAD file was created using an application other than Autocad (we have seen that message).