Post backs are sometimes lost

At least one of our thousands of users cannot use the forms in the web page. When he post backs the form the web page comes back with the same content as before the post. My guess it is probably just reloaded from database - which means the server did not understand a post back was made. It works for pretty much everyone and I know there are no problems in code that can cause this problem. Site is ASP.NET 4.0, 2008R2. Customer uses IE7.

I found a similar q/a here: POST data getting lost: Content Length = 0

Problem is that I am not able to go to customer and do testing myself. So my question is, what other possible reasons can we come up wit开发者_StackOverflow中文版h for this?

I would be very happy for any feedback on the issue.