ASP.Net Ajax elements not being recognized

I've just installed ASP.Net Ajax beta 2 and added its references to web.config, but my project still gives me some errors (my project was originally created using ASP.Net Ajax beta 1 template).

Here they are:

Warning 1 The 'requirePermission' attribute is not declared. c:\Inetpub\wwwroot\n2_lc1\Web.config 7 206 c:\...\n2_lc1\
Warning 2 The 'requirePermission' attribute is not declared. c:\Inetpub\wwwroot\n2_lc1\Web.config 8 200 c:\...\n2_lc1\
Warning 3 The 'requirePermission' attribute is not declared. c:\Inetpub\wwwroot\n2_lc1\Web.config 9 214 c:\...\n2_lc1\
Error 28 Element 'ScriptManager' is not a known element. This can occur if there is a compilation error in the Web site. c:\Inetpub\wwwroot\n2_lc1\processo\acompanhamento_corrida.aspx 32 7 c:\...\n2_lc1\

What can I do?

When I create a new project it works. With existing projects it doesn't work.

Try to take a look at this reading when upgrading to Ajax Beta 2 -
????http://66.102.7.104/search?q=cache:6kV1ivEIoIYJ:ajax.asp.net/files/Migration%2520Guide.doc+Upgrade+Ajax+Migration&hl=en&ct=clnk&cd=1
????http://ajax.asp.net/files/AspNet_AJAX_CTP_to_Beta_Whitepaper.aspx
Wish the above can give you some helps.

Jasson, thanks for your reply, but the problem isn't migrating an Atlas to Ajax code. The problem I have is about the prefix ASP for Ajax controls that Visual Studio Intellisense is not recognizing.

Visual Studio marks the Ajax elements as unknown. Their elements only work if I change Ajax prefix to another one (different from ASP).

Sorry for not giving you an immediate reply.For your questions, try to follow up the following suggestions.

Do you have the following code line when you want to access Ajax control toolkit? This is necessary to refer to Ajax control toolkit in your website project. If not,try to add it