A potentially dangerous Request.Form value was detected from the client

I keep getting the above error even though ValidateRequest="false" in the page tag and

 ValidateRequestMode="Disabled" EnableEventValidation="false" in the controls included

and I have this in the web.config

<system.web>
      <httpRuntime requestValidationMode="2.0" requestPathInvalidCharacters="*,:" />

I suspect it is something to do with Ajax?  Anyone else still getting this error?