I am new to asp.net so i could be way off...
Is it possible that since performace can take a major hit when
debug=true,
that your control isn't yet loaded when you try to access it?
Maybe make your program wait for a sec?
Just a shot in the dark
jojoba

Hi  -

Take a look at the actual source your page is producing; is it
including the same javascript function multiple times?(once for each
instance of the control).

If so, this will also produce this error - you can't have more than
one JS function of the same name.

To get around this problem, you can either:

A) Generate the javascript dynamically, appending the ClientID to the
control after every reference of the function name (including the
function declaration)

B) Put the Javascript in a seperate file, and manually include this
file once on every page that uses your control. (do a search on client-
side includes)

Solution A is ideal if you plan on distributing the control amongst a
team or selling it. It's the better approach from a OOP point of view.
Unfortunately, by doing so, you end up with sloppy and overly verbose
HTML. Solution B) allows for cleaner output, but it might make you
scratch your head the next time you try to use this control.

You may be able to work with a third option wherein the controls
determine (through a shared variable, perhaps) whether or not there is
another control of the same type on the page, and whether or not the
client side include  has already been written out, but that may be
more complicated than your project mandates.

Good Luck,

-Mark