To see if a php error is occuring add the following code at line 1:
make sure not to leave any blank lines between this new code and the existing code on the page, or it will cause other errors.
if you could also send a copy of your page, that would be helpful
What is the file size of files you are trying to upload?
try using smaller files to see if maybe the issue is php server settings for uploaded file size.
if you are going to be uploading large files, you will need to modify the server settings to allow for large file uploads.
See the following page for details: