Couldn't find this anywhere, so I thought I'd post it... The AllowBlank parameter on TextFields doesn't trim spaces before validating, and as such would allow empty values. This will make a global validator in such cases:

Code:
Ext.apply(Ext.form.TextField.prototype,{ 
    validator:function(text){
        if(this.allowBlank==false && Ext.util.Format.trim(text).length==0)
          return false;
        else
          return true;
    }
});