It appears there is a bug in the code for the function WAValidateRQ in the most recent version of validation toolkit when doing client validation on a select list.
The code:
if (formElement.length) formElement=formElement[0];
should be:
if (formElement.length && inputType.toLowerCase()!="select") formElement=formElement[0];
You can correct the problem manually for now. I will make sure it is fixed in the next update.