>Not aure. I'd expect that,regardless of the cause of the corruption, if ViewState Validation is enabled then that should catch a problem before the deserializer kicks in. Only an assumption though.....

Well, for sure, the ViewState was enabled when that happened. Because, it's been a few days since I switched without that for only two minutes and put it back to its normal state after. My assumption is that this is not a perfect world and something might have slipped at the .NET framework level.