As I have blogged in one of my previous post, crystal reports tool bars have a strange behavior when used inside an update panel. The solution for this can be achieved by using a customized toolbar for CrystalReportViewer. Following blog provides such implementation using an example and it worked for me
http://www.rahulsingla.com/blog/2010/03/an-ajax-toolbar-for-asp-net-crystal-reports
http://www.rahulsingla.com/blog/2010/03/an-ajax-toolbar-for-asp-net-crystal-reports