Issue is that when there is RadComboBox inside update panel, memory leak occurs, same as if there is a TreeView control with context menus (this is important) enabled. Below I provide a link to a tool I used to profile, also a link to stand-alone web app project that reproduces the issue. Once the radcombobox is commented out and I remove context menus template from treeview - memory leak doesn't occur anymore. I'm using latest controls 2010.3.13.17.40 and web app is asp.net 4.0
Project details: you might need to add reference to Telerik.Web.UI.dll. (project is messy, cause it's a testing sandbox, also it's set up to run on my IIS 7.5 as localhost:1234 <- you will need to change this)
Next, profile (click some buttons, do drag'n'drop treeview elements) the page with given tool, you will see leaks count and browser memory consumption will be constantly increasing.
How to stop leaking:
go to: MainHeader.ascx and fully comment out <telerik:RadComboBox ID="ddlOwnProjects" runat="server"
then go to: Default.aspx and comment out <ContextMenus> for <telerik:RadTreeView ID="tree" runat="server"
rebuilt site, restart profiling application (totally restart to reset #leaks), click on buttons, try drag'n'drop tree items - #leaks - will remain 0.
I'm developing fully ajaxified asp.net 4.0 application and leaks there increase ~100-200 objects per single postback, slowly-slowly browser starts consuming more and more memory.
Please verify this and let's find the solution.
Link to the web app: leaking project
IE Sieve from http://home.orange.nl/jsrosman/
P.S.: would be great to have opportunity to upload zip files directly here