The assignment module does not show all uploaded files in the grading view (Windows 2008 R2, IIS).
After debugging php/checking the html we have found the cause: duplicate IDs.
Hotfix: modify ".uniqid" call in mod/assign/renderer.php (pass '', true to call).
Details/Hotfix: see Attachment
Interestingly we have cloned our moodle installation to another Windows 2008 R2 server (cloned the moodle directory, the php installation and the moodle datastore and configured the same iis settings) but only our productive machine produced duplicate ids and we couldn't figure out the difference between the two servers (same os, same windows patch level, same server roles, same iis version/settings/appPool settings, same php version/php.ini, ...).