Help reading stack trace error

I'm having a problem that I cannot figure out. Any help is greatly appreciated.
Overview: We have a gallery area where users can submit an image along with a description and these get reviewed by an admin, who can approve or delete the post). The admin deleted a post, and now the gallery admin page is broken and throws the error below.
Can anyone point me in the right direction?
System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. Parameter name: index at System.Data.Linq.EntitySet`1.get_Item(Int32 index) at System.Data.Linq.EntitySet`1.System.Collections.IList.get_Item(Int32 index) at System.Web.UI.DataBinder.GetIndexedPropertyValue(Object container, String expr) at System.Web.UI.DataBinder.Eval(Object container, String[] expressionParts) at ASP.admin_warmoth_gallery ...