Using Ajax Toolkit

[David C]

I have an ASP.Net 2.0 website that I would like to use the latest Ajax
Toolkit (in particular the ListSearchExtender). I added the controls to my
VS 2005 Toolbox but when I try to run the web page I get the error below:

The type 'System.Web.UI.ScriptManager' is ambiguous: it could come from
assembly
'C:\WINDOWS\assembly\GAC_MSIL\System.Web.Extensions\1.0.61025.0__31bf3856ad364e35\System.Web.Extensions.dll'
or from assembly
'C:\WINDOWS\assembly\GAC_MSIL\System.Web.Extensions\3.5.0.0__31bf3856ad364e35\System.Web.Extensions.dll'.
Please specify the assembly explicitly in the type name.

Any idea how I can fix this? Also, when I upgrade to VS 2008 will I need to
do anything special to move my 2.0 sites to 3.5? Thanks.

David