If you are using the Download Manager it may be trying to reuse what was cashed. It might have even have trouble finishing and try an download the final bits of the file when you restart it. Try deleting what is cached then start the download again.
64-bit OS:
C:\Program Files (x86)\Common Files\Akamai\Cache
32-bit OS:
C:\Program Files\Common Files\Akamai\Cache
You might also try an alternative download method.
Douglas Lauritsen
Support Specialist
Product Support
Autodesk, Inc.