The Designer shows "Error creating contol - grdMembers. The type initializer for 'EO.Web.Internal.bl' threw an exeption"

The control seems to work OK but I cant add new columns...

<eo:Grid ID="grdMembers" runat="server"
BorderColor="#828790" BorderStyle="Groove"
BorderWidth="1px" ColumnHeaderAscImage="00050204"
ColumnHeaderDescImage="00050205"
ColumnHeaderDividerImage="00050203" ColumnHeaderHeight="24"
FixedColumnCount="1" Font-Bold="False" Font-Italic="False"
Font-Names="Tahoma" Font-Overline="False"
Font-Size="8.75pt" Font-Strikeout="False"
Font-Underline="False" GridLineColor="240, 240, 240"
GridLines="Both" Height="393px" ItemHeight="19"
ScrollBars="Vertical" Width="557px"
ClientSideOnItemCommand="OnItemCommand">
<FooterStyle CssText="padding-bottom:4px;padding-left:4px;padding-right:4px;padding-top:4px;" />
<ColumnTemplates>
<eo:TextBoxColumn AllowSort="True" HeaderText="First name"
Name="colFirstName" ReadOnly="True" SortOrder="Ascending"
TextBoxMaxLength="20">
<TextBoxStyle CssText="BORDER-RIGHT: #7f9db9 1px solid; PADDING-RIGHT: 2px; BORDER-TOP: #7f9db9 1px solid; PADDING-LEFT: 2px; FONT-SIZE: 8.75pt; PADDING-BOTTOM: 1px; MARGIN: 0px; BORDER-LEFT: #7f9db9 1px solid; PADDING-TOP: 2px; BORDER-BOTTOM: #7f9db9 1px solid; FONT-FAMILY: Tahoma" />
</eo:TextBoxColumn>
<eo:TextBoxColumn AllowSort="True" HeaderText="Last Name"
Name="colLastName" ReadOnly="True" SortOrder="Ascending"
TextBoxMaxLength="30">
</eo:TextBoxColumn>
<eo:TextBoxColumn AllowSort="True" HeaderText="Email"
Name="colEmail" ReadOnly="True" SortOrder="Ascending"
TextBoxMaxLength="40">
</eo:TextBoxColumn>
<eo:EditCommandColumn HeaderText="Edit" Name="colEdit">
</eo:EditCommandColumn>
<eo:DeleteCommandColumn>
</eo:DeleteCommandColumn>
</ColumnTemplates>
<ColumnHeaderStyle CssText="background-image:url('00050201');padding-left:8px;padding-top:4px;" />
<ItemStyles>
<eo:GridItemStyleSet>
<ItemStyle CssText="background-color: white" />
<ItemHoverStyle CssText="background-image: url(00050206); background-repeat: repeat-x" />
<SelectedStyle CssText="background-image: url(00050207); background-repeat: repeat-x" />
<CellStyle CssText="padding-left:8px;padding-top:2px;white-space:nowrap;" />
</eo:GridItemStyleSet>
</ItemStyles>
<ColumnHeaderHoverStyle CssText="background-image:url('00050202');padding-left:8px;padding-top:4px;" />
<Columns>
<eo:TextBoxColumn AllowSort="True" DataField="MembershipNumber"
DataType="Integer" HeaderText="Mbr.No" Name="colMemberNo"
ReadOnly="True" SortOrder="Ascending" TextBoxMaxLength="10"
Width="50" StyleField="align=left">
<CellStyle CssText="" />
</eo:TextBoxColumn>
<eo:TextBoxColumn AllowSort="True" DataField="FirstName"
DataType="String" HeaderText="First Name"
Name="colFirstName" ReadOnly="True" SortOrder="Ascending"
TextBoxMaxLength="20">
</eo:TextBoxColumn>
<eo:TextBoxColumn AllowSort="True" DataField="LastName"
DataType="String" HeaderText="Last Name" Name="colLastName"
ReadOnly="True" SortOrder="Ascending" TextBoxMaxLength="30"
Width="150">
</eo:TextBoxColumn>
<eo:TextBoxColumn AllowSort="True" DataField="CompEmail"
DataType="String" HeaderText="Email" Name="colEmail"
ReadOnly="True" SortOrder="Ascending" TextBoxMaxLength="40"
Width="200">
</eo:TextBoxColumn>
<eo:ButtonColumn ButtonText="Edit"
Name="btnEdit" Width="40">
<ButtonStyle CssText="" />
</eo:ButtonColumn>
</Columns>
</eo:Grid>