Error "System.Xml.Schema.XmlSchemaException" when making a connection, after making some settings (4276122)

Made some settings changes but when closing and re-launching Toad, the following error comes up for any connection attempted:

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Exception Information
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Exception: System.Xml.Schema.XmlSchemaException
Message : The 'http://www.quest.com/2010/15/04/Quest.PersistentCache:CustomDateRange' element is not declared.
Stack Trace:
at System.Xml.Schema.XmlSchemaSet.InternalValidationCallback(Object sender, ValidationEventArgs e)
at System.Xml.Schema.BaseProcessor.SendValidationEvent(XmlSchemaException e, XmlSeverityType severity)
at System.Xml.Schema.BaseProcessor.SendValidationEvent(XmlSchemaException e)
at System.Xml.Schema.Compiler.CompileElement(XmlSchemaElement xe)
at System.Xml.Schema.Compiler.CompileParticleElements(XmlSchemaComplexType complexType, XmlSchemaParticle particle)
at System.Xml.Schema.Compiler.CompileParticleElements(XmlSchemaComplexType complexType, XmlSchemaParticle particle)
at System.Xml.Schema.Compiler.CompileComplexTypeElements(XmlSchemaComplexType complexType)
at System.Xml.Schema.Compiler.Compile()
at System.Xml.Schema.Compiler.Execute(XmlSchemaSet schemaSet, SchemaInfo schemaCompiledInfo)
at System.Xml.Schema.XmlSchemaSet.Compile()
at System.Data.DataSet.ReadXSDSchema(XmlReader reader, Boolean denyResolving)
at System.Data.DataSet.ReadXml(XmlReader reader, Boolean denyResolving)
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