Invalid view state exception in asp.net. do you know any solution?
<p>this problem make me crazy!
i have asp.net website it raise periodically this error (in IE8):</p>

<pre><code>    System.Web.HttpException: Invalid viewstate.
       at System.Web.UI.Page.DecryptStringWithIV(String s, IVType ivType)
       at System.Web.Handlers.AssemblyResourceLoader.System.Web.IHttpHandler
.ProcessRequest(HttpContext context)
    ,...
</code></pre>

<p>or (in IE6)</p>

<pre><code>System.FormatException: Invalid length for a Base-64 char array.
   at System.Convert.FromBase64String(String s)
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
</code></pre>

<p>or (in IE7)</p>

<pre><code>System.FormatException: Invalid character in a Base-64 string.
   at System.Convert.FromBase64String(String s)
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
</code></pre>

<p>i set enableViewStateMac in web.config to false and defined machinekey in my web.config and defined UTF-8 encoding for every page 
but i received this errors.</p>

<p><bR/>
do you have any solution?
<br/>
best regards</p>
