Thread:Project:Support desk/File upload failures 'Could not find file "C:\WINDOWS\Temp\phpD9F.tmp'

MediaWiki 1.15.1, php 5.x Win 2005 IIS 6

When trying to upload a file, the server reports an error that it can not find the file. PHP scripts other than MediaWiki have no troubles on the server otherwise. But I can't figure out where the error is being generated. I have inserted 'file_exists' checks and, indeed, the temp file does not exist (duh!). This just started happening. Prior to this date, all users were successful uploading files. What would cause this? I HAVE TO FIX THIS SOON!