

You can always try to restart the IIS site or services, see if that helps. If you have a single user having this problem internally and with multiple browsers, I would say 99% sure, corrupt TCP stack on the end users machine.

Test in Firefox same problem? If no problem in Firefox, security settings are too aggressive. If you have multiple users, using IE having this problem, only in IE, the admin set the GPO for IE incorrectly, and could be blocking some ActiveX or scripts that need to run.
