There could be a couple of problems here.
1) The web server could use some additional configuration.
To see if that may be the problem, upload one of the AutoDesk sample DWF
files onto the server at the same location as your other file and change the
file name in your ASP page. If the DWF opens fine, the server is configured
properly. if not, then you may need to have the dwf mime type added to the
web server.
2) The DWF may have some bad data in it causing the download and display to
fail when the DWF is on a web server. These types of DWF's load fine when
opened from your system, but when streamed from a web server could cause the
viewer to hang when opening or crash. If the sample file opens fine on your
web site, we may have to look further into the DWF itself to see if there's
something wrong with it.
--
John Schmier
Autodesk DWF QA