>Looks right.
>Not sure whether it would make a difference but I see that although you are targeting ASP.NET 4 you have the requestValidationMode="2".
>The documentation isn't very clear but it seems that when set to '2' validation is only applied to pages (and even then can be suppressed on individual pages). You could try removing that attrib (or setting it to "4")
>But (and I keep coming back to this) you really must determine whether the method is simply not being called or whether it is being called but not behaving as expected. Set a break point, throw an exception, write to the event log, whatever.......

In your test, you were able to bypass the IIS default message by taking priority over it and applying business logic and/or redirecting to another page?

I did a test with requestValidationMode="4" but that did not change anything.

I think I have found a memory issue while doing those tests. I will let you know later on about my results.