Are you running FoxWeb as a service?  If yes, then you must make sure that the user that the sservice is running as has read and write privileges to c:\temps.  The IUSR account, which is what creates the POST file also needs read and write privileges in the same location.  The simplest way to achieve this is to right-click on the c:\temp directory in Windows Explorer, select properties, Security and then give full rights to "Everyone".