Using an event to set some text box values in your report is probably the main issue here.
It is not recommended to use events in your reports. This is often mentioned by Telerik staff in the forums and in their help: http://www.telerik.com/help/reporting/report-events.html
(the first line).
Also you are not doing it correctly, because you are accessing the report items by their definition inside an event and you should be accessing the processing items. There is a difference explained here: http://www.telerik.com/help/reporting/designing-reports-life-cycle.html
and also here: http://www.telerik.com/help/reporting/faq-accessing-items.html