"Invalid URI: The hostname could not be parsed" when clicking Database Explorer's table tab (4278638)

User connected to database from Toad for DB2. When the user clicked on the Database Explorer's Table tab, it listed only one table (there are more tables on that schema), an error popped up Invalid "URI: The hostname could not be parsed."
Stack Trace:

at System.Uri.CreateThis(String uri, Boolean dontEscape, UriKind uriKind)
at System.Uri..ctor(String uriString, UriKind uriKind)
at System.Xml.XmlResolver.ResolveUri(Uri baseUri, String relativeUri)
at System.Xml.XmlUrlResolver.ResolveUri(Uri baseUri, String relativeUri)
at System.Xml.XmlTextReaderImpl..ctor(String url, XmlNameTable nt)
at System.Xml.XmlTextReader..ctor(String url)
at System.Data.DataSet.ReadXml(String fileName)
at Quest.PersistentCache.DataEngine.LoadDataSet()
at Quest.PersistentCache.DataEngine.Contains(String id, DimensionTypes dimensionType)
at Quest.PersistentCache.PersistentCache.Contains(String id, DimensionTypes type)
at Quest.Toad.DatabaseBrowser.ObjectPaletteControl.SetNodeImage(TreeListNode node, ITrl trl)

at Quest.Toad.DatabaseBrowser.ObjectPaletteControl.TrlUpdated(ITrl listtrl, TrlCollection trls, Boolean clear, Boolean done)
at Quest.Toad.DatabaseBrowser.ObjectPaletteControl.ReadTrl(ITrl trl)
at Quest.Toad.DatabaseBrowser.ObjectPaletteControl.updateContentTimer_Tick(Object sender, EventArgs e)
at System.Windows.Forms.Timer.OnTick(EventArgs e)
at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)