Blah – I hate stupid error messages. Basically everywhere you look to see what causes this, it has something to do with cacading drop downs. I have ran into this error twice and the fix is – change a “=” to a “#”

if you have in your aspx page
<%= GetMyInfo(Eval("Blah").ToString()) %>

it will throw that error if it is in a repeater or data control. Change it to

<%# GetMyInfo(Eval("Blah").ToString()) %>

and viola! it works :)