>>They both are 3.5.0 already. However, several other references are 2.0 Should I try to update them?
>
>No, that shouldn't be necessary. Most of the other references haven't been updated to a 3.5-specific version.
>
>Did you upgrade the AjaxControlToolkit as well? If not, that's probably the source of your error.
>

How exactly should I update it? I thought everything is included with the installation.

The version says BIN AutoUpdate.

>>
>>Also why do I need Windows Form in a WEB application?
>
>I've noticed that as well, but I've never had time to investigate it.
>

I removed it and it seems to build the application Ok. I also removed Microsft VBScript.

>>
>>Do you know how can I copy the references and their versions, BTW? This dialog doesn't seem to allow copy them.
>>
>
>Sorry, no.