It the problem is the amount of time that it takes to see any result then the issue is likely a timeout problem. This can occur as a result of the size of the upload since the checks on the file type do not occur until the file has been uploaded to it's temporary location on the server.
On your page you can expand the bindings for the file upload and put the full debugging binding on the page then run the test again. It should let you know if there is an error with the upload.
If the problem is just a timeout issue you can increase the execution time either by updating the php.ini file or by adding in this code to the page:
set_time_limit(<number of seconds to increase time limit by>);