There is a known issue with streaming content from a container field in a web published database that applies to both Instant Web Publishing and WebDirect. See if this bug applies to your situation:
For More Information see: Contents streaming to internet is impossible over IWP
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip
Thanks for the help Phil. Turns out this was a deployment issue on server. (Not even really Filemakers fault). At some point websites got turned on in the OS X server app. This activated OS X's implementation of Apache which was configured to operate on the same ports as Filemaker's internal version of Apache. Filemaker serves interactive content as an HTTP stream. When the client would request the interactive content on port 80, OS X, not Filemaker Server would reply and return the 404 error.