Upgrade to Visual Studio 2015 gives false errors

Question

I have upgraded a project from VS 2012 to VS 2015 and I am getting bizarre errors. On some windows it complains about Color and Brush definitions even though I am doing absolutely nothing with any colors or brushes. The project will compile but the editor gives errors. As an example, on the XAML code:

    <ComboBox x:Name="cbCountry" Grid.Column="1"   VerticalAlignment="Bottom"  Height="28" FontSize="12" SelectionChanged="cbCountry_SelectionChanged" 
              HorizontalContentAlignment="Stretch" IsEditable="True" StaysOpenOnEdit="True" IsManipulationEnabled="True" KeyUp="cbCountry_KeyUp" />

complains about the color. Huh? What color? This is a pretty vanilla page with nothing fancy going on, anybody have any ideas how to eliminate these errors?

Update I had some windows resources defined as:

<Window.Resources>
    <DataTemplate x:Key="CityTemplate">
        <StackPanel Orientation="Horizontal">
            <Border BorderThickness="1" BorderBrush="Black">
                <TextBlock Text="{Binding City}" />
            </Border>
        </StackPanel>
    </DataTemplate>
</Window.Resources>

which does have a BorderBrush defined, but not for the combo. I tried taking a piece out at a time starting with the BorderBrush. It wasn't until I completely removed the <Windows.Resources> section that the error went away. Does anyone see anything wrong in the Windows Resources to cause this?

Update 2
The problem seems to be independent of any code behind. The entire XAML is below:

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
        xmlns:ig="http://schemas.infragistics.com/xaml" 
        x:Class="PTHWPF.View.Lookup" 
        Title="Lookup Place of Birth" Height="400" Width="600" Loaded="Window_Loaded" 
        Icon="/PTHWPF;component/Resources/Images/LookupMap.png">
    <!--TextBlock.TextAlignment="Center" -->
<Window.Resources>
        <DataTemplate x:Key="CityTemplate">
            <StackPanel Orientation="Horizontal">
                <Border BorderThickness="1" BorderBrush="Black">
                    <TextBlock Text="{Binding City}" />
                </Border>
            </StackPanel>
        </DataTemplate>
    </Window.Resources>
    <Grid IsManipulationEnabled="True" >
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="110" />
            <ColumnDefinition Width="280*" />
            <ColumnDefinition Width="180*" />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="60" />
            <RowDefinition Height="50" />
            <RowDefinition Height="50" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <Label Content="Country or State" Height="28" HorizontalAlignment="Right"  x:Name="lbCountry" VerticalAlignment="Bottom" />
        <ComboBox x:Name="cbCountry" Grid.Column="1"   VerticalAlignment="Bottom"  Height="28" FontSize="12" SelectionChanged="cbCountry_SelectionChanged" 
                  HorizontalContentAlignment="Stretch" IsEditable="True" StaysOpenOnEdit="True" IsManipulationEnabled="True" KeyUp="cbCountry_KeyUp"  >
        </ComboBox>
        <Label Content="City" Grid.Row="1" Height="28" HorizontalAlignment="Right"  x:Name="lbCity" VerticalAlignment="Bottom" />
        <ig:XamMultiColumnComboEditor SelectionChanged="cbCity_SelectionChanged"
            Grid.Column="1" Grid.Row="1" 
            HorizontalAlignment="Stretch" 
            x:Name="cbCity" Height="28" 
            VerticalAlignment="Bottom" 
            DataContext="{Binding}" 
            DisplayMemberPath="City" 
            HorizontalContentAlignment="Left" 
            IsTabStop="True" MinWidth="250" 
            FilterMode="FilterOnPrimaryColumnOnly"/>
        <DockPanel Grid.Column="1" Grid.Row="2" HorizontalAlignment="Center" >
            <Button Background="#9F7F90FC" Height="30" x:Name="btnOk" Width="80" Style="{DynamicResource RoundedButton}" HorizontalAlignment="Left" IsDefault="True" Click="btnOk_Click" VerticalAlignment="Bottom" Margin="0,0,20,0">
                <StackPanel Orientation="Horizontal">
                    <Image Height="20" Source="/PTHWPF;component/Resources/ok.png" Width="20" />
                    <AccessText Margin="5,3,0,0" x:Name="btnOkText" Text="_Ok"/>
                </StackPanel>
            </Button>
            <Button Background="#9F7F90FC" BorderBrush="#95FFFFFF" Height="30" x:Name="btnCancel" Style="{DynamicResource RoundedButton}" Width="80" IsCancel="True"  Click="btnCancel_Click" VerticalAlignment="Bottom" HorizontalAlignment="Right" Margin="20,0,0,0">
                <StackPanel Background="{x:Null}" Orientation="Horizontal">
                    <Image Height="20" Source="/PTHWPF;component/Resources/Images/cancel.png" Width="20" />
                    <AccessText Margin="5,3,0,0" x:Name="btnCancelText" Text="_Cancel"/>
                </StackPanel>
            </Button>
        </DockPanel>
    </Grid>
</Window>

Answer 1

Apparently Visual Studio 2015 Enterprise Edition had some issues, this also included "Handler=..." errors such as found here: https://connect.microsoft.com/VisualStudio/feedback/details/1611888/xaml-editor-error-invalid-value-for-property-handler-and-ischecked-bug-remains-in-the-enterprise-version-of-vs-2015

I encountered it as well on other XAML files, but it didn't cause the designer to fail.

Solution:
Upgrade to Service Pack 1 found here:
https://www.visualstudio.com/en-us/news/vs2015-update1-vs.aspx

It is a web update and it took over an hour to do. I will also require a reboot of windows to finish, so keep that in mind. Hopefully anyone finding this post won't spend days like I did to fix the problem.