Proxy problem with standalone on a users computer

[gmccarthy]

I have a standalone (LC 7.1.1) that another person uses on their windows computer.
It works properly on some computers but not all.
The program attempts to POST to a dropbox api but is unable to on some computers.
Testing showed that the program can ping the dropbox api website: api.v.dropbox.com
The user reports that there are no proxies set.
The failed POST attempt produced a log showing:

_proxyForURL_proxyForURL use _proxyFromHTTPProxy() with HTTPProxyProxy for URL: http://:80
Any ideas what I might be able to do?

[gmccarthy]

I discovered that the HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Connections\DefaultConnectionSettings entry contained a reference to a pac file but the HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Connections\AutoConfigURL was empty.
I doesn't look like the pac file reference in the DefaultConnectionSettings is being used in libUrl.
Would this be the cause of not being able to connect to the dropbox api website?