We're using Telerik Reporting Q2 2009 (dll version: 3.1.9.807) and we're having trouble rendering Grave Accents " ` " and Acute Accents " ยด " inside of a HTMLTextBox control.
I have not been able to reproduce the problem you describe (see attached video). We had some problems with accent characters in the report designer, but they have been resolved in Q2 (see release notes). We've however never had any reports about problems with such characters in runtime.