I found the solution to the feedbrowser problem in my case. In the settings for the Feedbrowser, the values of the Themes, platinum and graphite are lowercase, but need to be Title case in order to match the css classes in the javascript and css files.
In:
admin/syndication/feedbrowsersettings.ascx
Change:
<asp:DropDownList id="Theme" runat="server" CssClass="NormalTextBox" Width="250px">
<asp:ListItem Value="platinum">Platinum</asp:ListItem>
<asp:ListItem Value="graphite">Graphite</asp:ListItem>
</asp:DropDownList>
to
<asp:DropDownList id="Theme" runat="server" CssClass="NormalTextBox" Width="250px">
<asp:ListItem Value="Platinum">Platinum</asp:ListItem>
<asp:ListItem Value="Graphite">Graphite</asp:ListItem>
</asp:DropDownList>