Invalid postback or callback argument

[Ana]

Hi,

In my page I have a GridView and in two columns the user has the
option to send an email by clicking a button (so, I have two buttons:
SendEmail1 and SendEmail2). When clicking in one of these buttons, the
email is sent correctly. However, if immediately after send an email
the user try to send the other one (by clicking the other button), the
following error message is fired:

Invalid postback or callback argument. Event validation is enabled
using <pages enableEventValidation="true"/> in configuration or <%@
Page EnableEventValidation="true" %> in a page. For security
purposes, this feature verifies that arguments to postback or callback
events originate from the server control that originally rendered
them. If the data is valid and expected, use the
ClientScriptManager.RegisterForEventValidation method in order to
register the postback or callback data for validation.


I remember I had this same error message before but I don't remember
the context. Does anyone know why this message was fired? What is
happening? How to fix it?

Thanks a lot,

Ana

[Ana]

An update to this problem: the error message is fired when I try to
send another email, no matter if I'm trying to resend the same email
or if I'm trying to send another email.

[Ana]

Because I need to re-bind the GridView after sending the email, my
problem was solved. However, I would like to understand what was
happening and why that error message was being fired...