I went into the .browser file and removed the following line:

<adapter controlType="System.Web.UI.WebControls.TreeView" adapterType="CSSFriendly.TreeViewAdapter" />

It works now.

Is there a way to get it to work with the Adapter? I'd still like to know the cause of the issue. I also tried disabling viewstate for the page and it worked then too.

Kosmo