ASP.NET ScriptManager-based AJAX calls to web service failing

We have a gaming application in which clients, all running IE make calls to web services using the API genera开发者_开发知识库ted by the ASP.NET ScriptManager.

After a certain period of time, we start getting failures, with Fiddler showing the following error coming back from the server:

Connection to xxx.yyy.net failed.

Exception Text: Only one usage of each socket address (protocol/network address/port) is normally permitted

We are not in control of the server's hardware, so altering the TCP/IP settings is not an easy option. Anyone have thoughts on how to deal with this?

This blog post seems relevant.

"Here is the scoop 1. When you make authenticated calls, the client is closing connections. And when you are making authenticated calls repeatedly to the same server, you are making and closing connections repeatedly 2. The same might happen when you are making regular http [un authenticated] calls but setting keep-alive = false."

http://blogs.msdn.com/b/dgorti/archive/2005/09/18/470766.aspx