I have a usercontrol with asp:textbox controls on it that also performs postbacks. If two users, who are both identified by a different session variable, postback the page within the same second, one user will see the other user's viewstate values in the text boxes. I have validated that this happens by setting a textbox, a session variable, and a cookie to the same value (the same value that identifies the user) and writing to the log when all three don't match. The text box's value is the one that is logged as the other user's value.

ASP.net 3.5, IIS 6

Has anyone experienced this issue.