Commented Issue: MaskedEditExtender loses value [27920]

MaskedEditExtender works fine when user enters a value then exits the textbox.
However, I have a situation where a textbox is filled by code:
PhoneTextbox.Text = "6105551234" (value found in database, but is user editable)

When the textbox is displayed it is blank! Am I missing something?

Here is the Textbox definition:
<asp:TextBox ID="PhoneTextBox" runat="server" MaxLength="10" Columns="13" Visible="False"> </asp:TextBox>
<cc1:MaskedEditExtender ID="PhoneMaskedEdit" runat="server" Enabled="True" Mask="(999) 999-9999"
MaskType="Number" TargetControlID="PhoneTextBox" CultureAMPMPlaceholder=""
CultureCurrencySymbolPlaceholder="" CultureDateFormat="" CultureDatePlaceholder=""
CultureDecimalPlaceholder="" CultureThousandsPlaceholder="" CultureTimePlaceholder=""
ClearTextOnInvalid="false" >

Please help.

Thank you.

Comments: Thank you for checking. Getting a JavaScript error, so it is not expected to work properly. Below please find the error and a few lines of code around the offending line. Please advise how to proceed. Thank you. Unhandled exception at line 1241, column 5 in http://localhost:59267/ScriptResource.axd?d=-qISl4-OkT-7X02E4Fisr0hQIGUMq-eQ-3XIkCdYWEU47b7hWbcApWDrjA_0mTO37DVETwClVxYKedlLihic7ipA_PkUqyHZYxt4qKcwE9AFeF1p0&t=ac64ff3 0x800a1391 - JavaScript runtime error: 'console' is undefined Sys.Extended.UI.ScrollBars.registerEnum("Sys.Extended.UI.ScrollBars", false); var isUnminified = /param/.test(function(param) {}); Sys.Extended.Deprecated = function (oldMethodName, properMethodName) { if (isUnminified && console && console.warn) if(arguments.length == 1) console.warn(oldMethodName + " is deprecated."); else console.warn(oldMethodName + " is deprecated. Use " + properMethodName + " instead."); } Sys.Extended.UI.zIndex = function() {}; Sys.Extended.UI.zIndex.BubbleChartTooltip = 10000; Sys.Extended.UI.zIndex.ComboBoxList = 10000; Sys.Extended.UI.zIndex.DropWatcherDragVisual= 99999; Sys.Extended.UI.zIndex.LineChartTooltip= 10000; Sys.Extended.UI.zIndex.MaskedEditDivTip = 99999; Sys.Extended.UI.zIndex.ModalPopupBackground = 10000; Sys.Extended.UI.zIndex.PasswordStrengthTextDisplay = 10001; Sys.Extended.UI.zIndex.Popup = 1000; Sys.Extended.UI.zIndex.SeadragonContainer = 99999999; Sys.Extended.UI.zIndex.SliderDragHandle = 999;