DropDownList SelectedIndexChanged Event not fired

[Guest]

Hi,
I've seen this posted many times but still can't find any answer. I have a
number of ddl in my form and only one of them has the SelectedIndexChanged
Event fired correctly even if they all have their AutoPostBack property set
to true. They are all the same in regards to the properties and the methods
that populate them. My question is: is there a limit a web form can hold as
far as the number of controls having their EnableViewState properties set to
true? And ultimately, is there a way to make sure the event is triggered
correctly?

Thanks,