I think this happens because disabled controls are not posted back to the server (thus preventing detection of the postback).
You should make the controls Readonly
. Or re-enable them client-side just before posting.
See http://www.w3.org/TR/html401/interact/forms.html#adef-disabled
Disabled controls cannot be successful.
and, http://www.w3.org/TR/html401/interact/forms.html#adef-readonly
Read-only elements may be successful.