Have you seen this blogpost by EPiServers Sebastian Lundh:
Matbe it will help you?!
We are facing the same problem though we still run CMS R1 but since we upgraded to sp3 we had to upgrade to run .net ajax 3.5 to get X3 to work. This however made both ImageVault and EPiMail to stop function. I don't recieve the ambigous error report but only this:
Parser Error Message: The base class includes the field 'scriptManager', but its type (System.Web.UI.ScriptManager) is not compatible with the type of control (System.Web.UI.ScriptManager).
Anyone found a solution to this? Or else we need to downgrade ajax version again and skip using X3 again.
Good news, now the new version of EPiServer Mail is out. This version supports R2 and ASP.Net 3.5.
Go and get at the download section:
Im having some trouble installing EPiServer Mail 4.3 properly. We are running CMS 5 R2 3.5NET, but i keep getting errors like:
The server tag 'asp:ScriptManager' is ambiguous. Please modify the associated registration that is causing ambiguity and pick a new tag prefix.
The base class includes the field 'scriptManager', but its type (System.Web.UI.ScriptManager) is not compatible with the type of control (System.Web.UI.ScriptManager).
I have removed all references to version 1.0.61025.0, but still getting the same errors.
I looked in the user controls for EPiServer Mail, and they are using the 1.0-version:
<%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" Namespace="System.Web.UI" TagPrefix="asp" %>
Im guessing this is not EPiServer Mail dependent, since it applies to ImageVault as well. Is it, and i sincerely hope, possibly to run under framework 3.5? And how do i make that possible?