Error message: Collection was modified; enumeration operation may not execute.

Url: http://kastorialeather.gr/skin.aspx?lang=en&itemtype=ProductCategory&itemid=F25A1216&action=view&E3A7B4A0=87B3CE14‡A5EB7956‡D8629F55‡AC528FE8‡B7A4127C‡74D7B762‡C67AB4B8‡0A1F5FFC&splitter_products_offset=0

Message: Collection was modified; enumeration operation may not execute.

   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   at ASP.skin_aspx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in c:\inetpub\vhosts\kastorialeather.gr\skin.aspx:line 219
   at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
   at System.Web.UI.Page.Render(HtmlTextWriter writer)
   at Bone.Asp.RenderSkin(TextWriter w) in C:\Bone\Bone\src\Classes\Asp.cs:line 71
   at Bone.ModalAction.RenderPage(TextWriter w) in C:\Bone\Bone\src\Actions\Modal.cs:line 81
   at Bone.Asp.Render(HtmlTextWriter w) in C:\Bone\Bone\src\Classes\Asp.cs:line 82
   at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)