post data lost in transit from IE8 to IIS

I have a very strange problem with post data being lost in transit. The log-in form for our ASP web app has a for submitting the username / password. The ASP page then receives this post, checks the credentials, and re-directs successful log ins. The problem I'm seeing is that intermittently the post data is just dropped. The request appears on the server, but there is no data. Client side is IE8, server side is IIS running ASP. The user will be fine for a time, and then as soon as they get his er开发者_如何转开发ror, they have to restart the machine to solve it. What could be causing this and what type of diagnostics can I run to locate the problem?

Use Fiddler tool for inspecting client-server http communication. Maybe something is dropping data between client and server.

You can save each request which you receive in server in some file and to see if they really does not send you nothing. Try to see IIS log for error. Maybe your IIS is busy with other requests and refuse to accept this one. Than it will send 500 error to the client.