WWW error: necessary data rewind wasn't possible [SOLVED]

I have a leaderboard on my web site that uses an ASP.Net web service which I wrote. I have two sites. One site runs W2K3 and IIS 6, and the other site runs W2K8 and IIS 7. I use the WWW class to communicate with my web service in order to register a player and upload scores.

On the system that is running W2K3 and IIS 6, everything works fine. On the system that is running W2K8 and IIS 7, I get the error, "necessary data rewind wasn't possible."

I ran Wireshark and analysed the packets between my game and the web service on IIS 7. I found that the sessionState in web.config was set to "cookieless=AutoDetect". This was causing the requests to the server to generate a HTTP 302 code (I think), and WWW didn't know how to respond. So I changed the web.config sessionState to "cookieless=false". Changing this setting solved the problem. On the system running IIS 6 the sessionState cookieless attribute is not configured and defaults to false apparently.

But now my web service will not work if someone's browser application has cookies disabled. I think it's a small price to pay considering that my game is calling the web service most of the time. I do have a leaderboard application running, and this could be a problem for those users who visit my site and have cookies disabled. I think that is a pretty small group of users and I am not worried about it.

I thought that this information was pretty important to post for other users.