Hi,

>>Can you reproduce the error by manually recycling the application pool?
>
>I had assumed that putting enableViewStateMac was doing it all in regards to that security. But, enableEventValidation and enableViewState also needed to be configured. Now, the page are responding extremely fast and are much smaller.
>
>I believe with those settings, I shouldn't have that error anymore.

I'm not sure how the EnableEventValidation setting would have any effect on a 'Invalid viewstate' error.

Setting EnableViewState to false would certainly stop to error since there would be no ViewState to validate <s>. But whilst you may not need to maintain ViewState on this particular page I assume there are other pages where this is not so - and those pages are probably still prone to the invalid viewstate error.

I'd suggest implementing the fixed key as recommended in the link Tracy supplied.