Oh mother tell your children not to do what I have done

Don't do this: Have a panel that uses an ajax CollapsiblePanel from the Ajax Control Toolkit, hide it by default, and then put a textbox inside the panel, and then put a requiredfieldvalidator on the textbox, and Then: expect any of your buttons to work! The result is that when the page loads, none of your buttons will work because the validator's validatin', which is good, but you can't see the validator's error message because it's in your collapsed panel, which is bad.

Here's a little search engine fodder: Datalist linkbutton button not posting back.