What do you mean by "field decorators" ? Is this applying css classes to fields?
This mean that fieldMissing / fieldInvalid css classes are not applied to inputs after false client validation.
I check it on the latest TimeTracker demo - http://opencomponentry.com:8080/timetracker/app
In Firefox false inputs are not highlighted any more.
In IE6 I get an error "Error validating TypeError : 'type' is null or is not an object"
I have this fixed but will probably need to wait until getting home to apply the changes to dojo.