title: Pesky "Invalid character in a Base-64 string." Exception
body: <p>Recently my application has been getting tons of these exceptions.</p>
  
  <p>I run ASP.net 3.5 on a Windows XP machine.  The exceptions tend to be random.  </p>
  
  <p>The application uses the Telerik RadControls for ASP.NET AJAX Q2 2010 SP1.</p>
  
  <p>The exception and StackTrace are below.</p>
  
  <pre><code>Exception Type: System.FormatException
  Message: Invalid character in a Base-64 string.
  StackTrace:  at System.Convert.FromBase64String(String s)
               at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)
               at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState)
               at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState)
               at System.Web.UI.SessionPageStatePersister.Load()
  </code></pre>
  
  <p>Any ideas on what could be causing this?  Also, this may or may not be related, often times pages with a decent amount of data (greater than 2 minutes load time) time out randomly.  I've increased the timeout for each of these long-loading pages in web.config...</p>
  
  <pre><code>&lt;location path="mypage.aspx"&gt;
   &lt;system.web&gt;
    &lt;httpRuntime executionTimeout="1920"/&gt;
   &lt;/system.web&gt;
  &lt;/location&gt;
  </code></pre>
  
  <p>Thanks for any help.</p>
  
  <p>-Daniel</p>