Index: umc/widgets/CheckBox.js
===================================================================
--- umc/widgets/CheckBox.js	(Revision 35029)
+++ umc/widgets/CheckBox.js	(Arbeitskopie)
@@ -65,6 +65,12 @@
 
 		_getValueAttr: function() {
 			return this.get('checked');
+		},
+
+		setValid(isValid, message) {
+			// a checkbox cannot be invalid
+			// (for now, we should consider implementing it!)
+			return false;
 		}
 	});
 });
Index: umc/widgets/_FormWidgetMixin.js
===================================================================
--- umc/widgets/_FormWidgetMixin.js	(Revision 35029)
+++ umc/widgets/_FormWidgetMixin.js	(Arbeitskopie)
@@ -116,6 +116,7 @@
 				this.set('invalidMessage', message);
 				this._maskValidSubsetError = false;
 			}
+			return true;
 		}
 	});
 });
Index: umc/widgets/Form.js
===================================================================
--- umc/widgets/Form.js	(Revision 35029)
+++ umc/widgets/Form.js	(Arbeitskopie)
@@ -456,8 +456,14 @@
 			}
 			deferred = deferred.then(lang.hitch(this, function(data) {
 				// fire event
-				this.onSaved(true);
-				return data;
+				if (data && parseInt(data.status, 10) == 201) {
+					// 201 is ridiculous...
+					this.onValidationError(data.result);
+					return data;
+				} else {
+					this.onSaved(true);
+					return data;
+				}
 			}), lang.hitch(this, function() {
 				// fire event also in error case
 				this.onSaved(false);
@@ -487,6 +493,24 @@
 			return widgets;
 		},
 
+		onValidationError(/*Object*/ data) {
+			// naive implementation
+			umc.tools.forIn(data, dojo.hitch(this, function(iwidget, error_msg) {
+				var worked = false;
+				try {
+					worked = this.getWidget(iwidget).setValid(false, error_msg);
+				} catch(e) {
+					console.log(iwidget, e);
+				}
+				if (!worked) {
+					umc.dialog.notify(error_msg);
+				}
+			}));
+			onSaved(false, data);
+
+			this.onSaved(false);
+		},
+
 		onSaved: function(/*Boolean*/ success) {
 			// event stub
 		},
Index: umc/store.js
===================================================================
--- umc/store.js	(Revision 35029)
+++ umc/store.js	(Arbeitskopie)
@@ -142,8 +142,14 @@
 		else {
 			return this._genericMultiCmd(type, [param]).
 				then(function(results) {
-					if (results && results instanceof Array) {
-						return results[0];
+					if (results)
+						if (results instanceof Array) {
+							// 200
+							return results[0];
+						} else {
+							// validation error in singleCmd (put, add, ...)
+							return {'status' : 201, 'result' : results['0']['object']};
+						}
 					}
 				});
 		}
@@ -156,7 +162,7 @@
 		}
 		else {
 			// send the UMCP command
-			return this.umcpCommand(this.storePath + '/' + type, params).
+			return this.umcpCommand(this.storePath + '/' + type, params, false).
 				then(/*REQUIRE:"dojo/_base/lang"*/ lang.hitch(this, function(data) {
 					// make sure that we get an non-empty array
 					//console.log('# _genericMultiCmd - deferred: data=' + String(data));