powerpoint 2007 Selection.TextRange Error when Selection is made in Table Object on a slide

moPowerPointApp.ActiveWindow.Selection.TextRange.Characters.Count

Above line gives an error called "The specified value is out of range." when the selection is made in a table object present in one of the ppt slide.

And above is working fine when I use 2003 object model.

Is there some substitute for the above change?

Its urgent. any help will subtract my problem.

Thanks!!!