Error message on Mod pages when trying to post a comment.

This is what it says to me when I try to post a comment on Mods, even if I am logged in:

Server Error in '/' Application.

Conversion from type 'DBNull' to type 'String' is not valid.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidCastException: Conversion from type 'DBNull' to type 'String' is not valid.

Source Error:

 An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[InvalidCastException: Conversion from type 'DBNull' to type 'String' is not valid.]
   Microsoft.VisualBasic.CompilerServices.Conversions.ToString(Object Value) +591
   MvLib.SingleMod.Comments_DataBound(Object sender, RepeaterItemEventArgs e) +961
   System.Web.UI.WebControls.Repeater.OnItemDataBound(RepeaterItemEventArgs e) +105
   System.Web.UI.WebControls.Repeater.CreateItem(Int32 itemIndex, ListItemType itemType, Boolean dataBind, Object dataItem) +142
   System.Web.UI.WebControls.Repeater.CreateControlHierarchy(Boolean useDataSource) +454
   System.Web.UI.WebControls.Repeater.OnDataBinding(EventArgs e) +53
   System.Web.UI.WebControls.Repeater.DataBind() +72
   MvLib.SingleMod.BindComments(Int32 ModID) +59
   MvLib.SingleMod.BindFull() +136
   MvLib.SingleMod.Page_Load(Object sender, EventArgs e) +56
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +47
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1061