KT,When you say "submit" are talking about clicking the "OK" button in the mediabin browser dialog (or double-clicking the image)? I just want to make sure we are not talking about the TeamSite's submit function that moves files into the STAGING area..
Is your DCT using "immediate" import or "deferred" import? The immediate import will download the file when the user presses the OK button (you will see a "Downloading, please wait..." message). The deferred import just grabs some of the information about the asset and stores it in the form.
Does the mediabin browser dialog window go away (close) when you click OK? Any additional details about what happens when this fails will be helpful.
You should check your TeamSite servletd (aka tomcat) log file for any error messages (/local/logs/iwui/servletd.log) when this happens. The name of log file differs slightly between windows an unix, but the directory path is the same.