Why can't I reply some comments in Acrobat 7.0 Pro, like text box?

I need to reply some comments. Some of the comments can not be "replied".

Is this is because the person wrote the comment was using a text box? How can I work around this?

thanks!

Why can't I reply some comments in Acrobat 7.0 Pro, like text box?

give me some more info... ok? ok!