We've recently been experiencing an SSRS (SQL Server 2008) report displayed in an ASP.NET web application using the ReportViewer control (Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a) hanging when rendering a report with over 100 rows and causing Internet Explorer (6, 7, 8) to use 100% (of one core) of CPU.
The report renders quickly in Firefox (and doesn't use high CPU).
The issue seemed to be caused by using the IE PNG Alpha fix (v2.0, by Angus Turnbull, http://www.twinhelix.com/).
We were using a cascading style sheet to apply the behaviour to all img and div tags:
img, div
{
behavior: url(script/iepngfix.htc)
}
Applying the behaviour to only the images we required resulted in the SSRS reports rendering quickly again.