This is happening only on one page where we have the below <telerik:RadGridView.RowDetailsTemplate> ..
taking this code block out and closing and reopening blend fixes it. Once the exception occurs in Blend .. all telerik RadGridView pages fail to render ..
<telerik:RadGridView IsReadOnly="True" AutoGenerateColumns="False" ShowGroupPanel="False" Grid.Row="2"
CanUserReorderColumns="False" CanUserResizeColumns="True"
RowIndicatorVisibility="Collapsed" IsFilteringAllowed="True" MaxHeight="400" MinHeight="40"
ItemsSource="{Binding TransactionProfileList, Mode=TwoWay}" telerik:StyleManager.Theme="Office_Blue"
GridLinesVisibility="None">
<telerik:RadGridView.Columns>
<telerik:GridViewToggleRowDetailsColumn />
<telerik:GridViewDataColumn x:Name="colSelect" Header="" TextAlignment="Center" IsFilterable="True">
..................................
.........................................
</telerik:GridViewDataColumn.CellTemplate>
</telerik:GridViewDataColumn>
</telerik:RadGridView.Columns>
<telerik:RadGridView.RowDetailsTemplate>
<DataTemplate>
<telerik:RadGridView IsReadOnly="True" AutoGenerateColumns="False" ShowGroupPanel="False" Grid.Row="2"
CanUserReorderColumns="False" CanUserResizeColumns="True" Width="1000"
RowIndicatorVisibility="Collapsed" IsFilteringAllowed="True" MaxHeight="300" MinHeight="40"
ItemsSource="{Binding Path=AccountDetails}" telerik:StyleManager.Theme="Office_Blue" GridLinesVisibility="None">
<telerik:RadGridView.Columns>
<telerik:GridViewDataColumn x:Name="AccountNumber" Header="AccountNumber" DataMemberBinding="{Binding Path=AccountNumber, Mode=TwoWay, Converter={StaticResource TextTrimByCharacter},ConverterParameter=23}" Width="200" ToolTipTemplate="{StaticResource AccountNumberTooltip}"/>
<telerik:GridViewDataColumn x:Name="BillToAddress" Header="BillToAddress" DataMemberBinding="{Binding Path=BillToAddress, Mode=TwoWay, Converter={StaticResource TextTrimByCharacter},ConverterParameter=30}" Width="200" ToolTipTemplate="{StaticResource BillToAddressTooltip}"/>
<telerik:GridViewDataColumn x:Name="ShipToAddress" Header="ShipToAddress" DataMemberBinding="{Binding Path=ShipToAddress, Mode=TwoWay, Converter={StaticResource TextTrimByCharacter},ConverterParameter=30}" Width="200" ToolTipTemplate="{StaticResource ShipToAddressTooltip}"/>
<telerik:GridViewDataColumn x:Name="Notes" Header="Notes" DataMemberBinding="{Binding Path=Notes, Mode=TwoWay, Converter={StaticResource TextTrimByCharacter},ConverterParameter=60}" Width="400" ToolTipTemplate="{StaticResource NotesTooltip}"/>
</telerik:RadGridView.Columns>
</telerik:RadGridView>
</DataTemplate>
</telerik:RadGridView.RowDetailsTemplate>
</telerik:RadGridView>
taking this code block out and closing and reopening blend fixes it. Once the exception occurs in Blend .. all telerik RadGridView pages fail to render ..
<telerik:RadGridView IsReadOnly="True" AutoGenerateColumns="False" ShowGroupPanel="False" Grid.Row="2"
CanUserReorderColumns="False" CanUserResizeColumns="True"
RowIndicatorVisibility="Collapsed" IsFilteringAllowed="True" MaxHeight="400" MinHeight="40"
ItemsSource="{Binding TransactionProfileList, Mode=TwoWay}" telerik:StyleManager.Theme="Office_Blue"
GridLinesVisibility="None">
<telerik:RadGridView.Columns>
<telerik:GridViewToggleRowDetailsColumn />
<telerik:GridViewDataColumn x:Name="colSelect" Header="" TextAlignment="Center" IsFilterable="True">
..................................
.........................................
</telerik:GridViewDataColumn.CellTemplate>
</telerik:GridViewDataColumn>
</telerik:RadGridView.Columns>
<telerik:RadGridView.RowDetailsTemplate>
<DataTemplate>
<telerik:RadGridView IsReadOnly="True" AutoGenerateColumns="False" ShowGroupPanel="False" Grid.Row="2"
CanUserReorderColumns="False" CanUserResizeColumns="True" Width="1000"
RowIndicatorVisibility="Collapsed" IsFilteringAllowed="True" MaxHeight="300" MinHeight="40"
ItemsSource="{Binding Path=AccountDetails}" telerik:StyleManager.Theme="Office_Blue" GridLinesVisibility="None">
<telerik:RadGridView.Columns>
<telerik:GridViewDataColumn x:Name="AccountNumber" Header="AccountNumber" DataMemberBinding="{Binding Path=AccountNumber, Mode=TwoWay, Converter={StaticResource TextTrimByCharacter},ConverterParameter=23}" Width="200" ToolTipTemplate="{StaticResource AccountNumberTooltip}"/>
<telerik:GridViewDataColumn x:Name="BillToAddress" Header="BillToAddress" DataMemberBinding="{Binding Path=BillToAddress, Mode=TwoWay, Converter={StaticResource TextTrimByCharacter},ConverterParameter=30}" Width="200" ToolTipTemplate="{StaticResource BillToAddressTooltip}"/>
<telerik:GridViewDataColumn x:Name="ShipToAddress" Header="ShipToAddress" DataMemberBinding="{Binding Path=ShipToAddress, Mode=TwoWay, Converter={StaticResource TextTrimByCharacter},ConverterParameter=30}" Width="200" ToolTipTemplate="{StaticResource ShipToAddressTooltip}"/>
<telerik:GridViewDataColumn x:Name="Notes" Header="Notes" DataMemberBinding="{Binding Path=Notes, Mode=TwoWay, Converter={StaticResource TextTrimByCharacter},ConverterParameter=60}" Width="400" ToolTipTemplate="{StaticResource NotesTooltip}"/>
</telerik:RadGridView.Columns>
</telerik:RadGridView>
</DataTemplate>
</telerik:RadGridView.RowDetailsTemplate>
</telerik:RadGridView>