Http Exception generated while validating viewstate
<p>I am getting the following error whenever I click on a postbacking control</p>

<pre><code>HttpException (0x80004005): Validation
of viewstate  MAC failed. If this
application is hosted by a Web  Farm
or cluster, ensure that  configuration
specifies the same validationKey and
validation  algorithm. AutoGenerate
cannot be used in a cluster.
</code></pre>

<p>I am not using a Web Farm or cluster server. I have even tried setting the page property <strong><em>EnableViewStateMac</em></strong> to false but it changes the error message stating</p>

<pre><code>The state information is invalid for 
this page and might be corrupted.
</code></pre>

<p>What could possibly be wrong?</p>
