<p>One of the sites I maintain relies heavily on the use of <code>ViewState</code> (it isn't my code). However, on certain pages where the <code>ViewState</code> is extra-bloated, Safari throws a <code>"Validation of viewstate MAC failed"</code> error.</p>

<p>This appears to only happen in Safari. Firefox, IE and Opera all load successfully in the same scenario.</p>

I've been doing a little research into this and whilst I'm not entirely sure its the cause I believe it is because Safari is not returning the full result set (hence cropping it).
I have been in dicussion with another developer and found the following post on Channel 9 as well which recommends making use of the SQL State service to store the viewstate avoiding the postback issue and also page size.
http://channel9.msdn.com/forums/TechOff/250549-ASPNET-ViewState-flawed-architecture/?CommentID=270477#263702
Does this seem like the best solution?