I have a user who is receiving a domain authentication prompt when trying to publish a website.  He has never been able to do this.

Several of his coworkers can publish with no problems.  When I look at all of their permissions on the IIS directory, they are the same.  They all have Modify rights on the IIS home directory.

 When the user having problems maps a drive to the folder he is trying to publish to, he can create new temp files manually and delete them.

 Can someone point me in the right direction to let me know what might be happening?

I have some additional information.  The user in question is able to publish by setting a target of a drive mapped to the directory.  He cannot publish when trying to set the following target:  http://<IP Address>:8050/<DirectoryName>.  As an example, he cannot publish to the following:  http://90.172.53.46:4025/TestDirectory.