"Multiple controls with same id.." shows shortly in IE tab

I have developed web control derived from CompositeDataBoundControl.
When i build the project, in IE tab for a very short time I get a message "Multiple controls with same ID.." and cannot read the rest of message.
I have enabled tracing, but everything seems fine. It seems that i generate two controls with same ID, but I don't know how to capture that message that is displayed shortly in IE tab.
Any suggestions?
Thanks.
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