diff --git a/config/alfresco/messages/webclient.properties b/config/alfresco/messages/webclient.properties
index 352496c3e1..0a2d687628 100644
--- a/config/alfresco/messages/webclient.properties
+++ b/config/alfresco/messages/webclient.properties
@@ -1765,6 +1765,7 @@ error_restore_search=Failed to restore saved search due to error: {0}
 error_shortcut_permissions=Unable to navigate to the item as it cannot be read by this user. Another user may have modified the permission.
 error_association=Failed to find association definition for association \"{0}\".
 error_charset_null=Null characterset value
+error_negative_quota=Quota cannot be negative: {0}
 
 # Confirmations
 return_to_application=Return to application
diff --git a/source/java/org/alfresco/web/bean/users/CreateUserWizard.java b/source/java/org/alfresco/web/bean/users/CreateUserWizard.java
index 9237ffa493..5a65dfab77 100644
--- a/source/java/org/alfresco/web/bean/users/CreateUserWizard.java
+++ b/source/java/org/alfresco/web/bean/users/CreateUserWizard.java
@@ -758,12 +758,20 @@ public class CreateUserWizard extends BaseWizardBean
                 if (logger.isDebugEnabled())
                     logger.debug("Created User Authentication instance for username: " + this.userName);
                 
-                putSizeQuotaProperty(this.userName, this.sizeQuota, this.sizeQuotaUnits);
+                if ((this.sizeQuota != null) && (this.sizeQuota < 0L))
+                {
+                    Utils.addErrorMessage(MessageFormat.format(Application.getMessage(context, UsersDialog.ERROR_NEGATIVE_QUOTA), this.sizeQuota));
+                    outcome = null;
+                }
+                else
+                {
+                	putSizeQuotaProperty(this.userName, this.sizeQuota, this.sizeQuotaUnits);
+                }
             }
             else
             {
-                outcome = null;
                 Utils.addErrorMessage(Application.getMessage(context, UsersDialog.ERROR_PASSWORD_MATCH));
+                outcome = null;
             }
             invalidateUserList();
         }
@@ -792,11 +800,19 @@ public class CreateUserWizard extends BaseWizardBean
     
     protected void putSizeQuotaProperty(String userName, Long quota, String quotaUnits)
     {
-       if ((quota != null) && (quota > 0))
+       if (quota != null)
        {
-          quota = convertToBytes(quota, quotaUnits);
+    	  if (quota >= 0L)
+    	  {
+    		  quota = convertToBytes(quota, quotaUnits);
+    	  }
+    	  else
+    	  {
+    		  // ignore negative quota
+    		  return;
+    	  }
        }
-
+       
        this.contentUsageService.setUserQuota(userName, (quota == null ? -1 : quota));
     }
     
diff --git a/source/java/org/alfresco/web/bean/users/EditUserWizard.java b/source/java/org/alfresco/web/bean/users/EditUserWizard.java
index d2d6f72b81..6c20e67bc5 100644
--- a/source/java/org/alfresco/web/bean/users/EditUserWizard.java
+++ b/source/java/org/alfresco/web/bean/users/EditUserWizard.java
@@ -205,14 +205,26 @@ public class EditUserWizard extends CreateUserWizard
             // TODO: RESET HomeSpace Ref found in top-level navigation bar!
             // NOTE: not need cos only admin can do this?
             
-            putSizeQuotaProperty(this.userName, this.sizeQuota, this.sizeQuotaUnits);
-            
+            if ((this.sizeQuota != null) && (this.sizeQuota < 0L))
+            {
+                Utils.addErrorMessage(MessageFormat.format(Application.getMessage(context, UsersDialog.ERROR_NEGATIVE_QUOTA), this.sizeQuota));
+                outcome = null;
+            }
+            else
+            {
+            	putSizeQuotaProperty(this.userName, this.sizeQuota, this.sizeQuotaUnits);
+            }
         }
         catch (Throwable e)
         {
             Utils.addErrorMessage(MessageFormat.format(Application.getMessage(FacesContext.getCurrentInstance(), ERROR), e.getMessage()), e);
             outcome = null;
         }
+        
+        if (outcome == null) {
+            this.isFinished = false;
+        }
+        
         return outcome;
     }
 }
diff --git a/source/java/org/alfresco/web/bean/users/UsersDialog.java b/source/java/org/alfresco/web/bean/users/UsersDialog.java
index f3996a0b81..baeb34734d 100644
--- a/source/java/org/alfresco/web/bean/users/UsersDialog.java
+++ b/source/java/org/alfresco/web/bean/users/UsersDialog.java
@@ -71,6 +71,7 @@ public class UsersDialog extends BaseDialogBean implements IContextListener, Cha
    public static String BEAN_NAME = "UsersDialog";
 
    public static final String ERROR_PASSWORD_MATCH = "error_password_match";
+   public static final String ERROR_NEGATIVE_QUOTA = "error_negative_quota";
    private static final String ERROR_DELETE = "error_delete_user";
    private static final String ERROR_USER_DELETE = "error_delete_user_object";
    
@@ -128,30 +129,32 @@ public class UsersDialog extends BaseDialogBean implements IContextListener, Cha
       return getUsers().size();
    }
    
-   public long getUsersTotalUsage()
+   public Long getUsersTotalUsage()
    {
-       long totalUsage = 0L;
+       Long totalUsage = null;
        List<Node> users = getUsers();
        for(Node user : users)
        {
            Long sizeLatest = (Long)properties.getUserUsage((String)user.getProperties().get("userName"));
-           if (sizeLatest != null)
+           if ((sizeLatest != null) && (sizeLatest != -1L))
            {
+        	  if (totalUsage == null) { totalUsage = 0L; }
               totalUsage += sizeLatest;
            }
        }
        return totalUsage;
    }
    
-   public long getUsersTotalQuota()
+   public Long getUsersTotalQuota()
    {
-       long totalQuota = 0L;
+       Long totalQuota = null;
        List<Node> users = getUsers();
        for(Node user : users)
        {
            Long sizeCurrent = (Long)user.getProperties().get("sizeQuota");
-           if (sizeCurrent != null)
+           if ((sizeCurrent != null) && (sizeCurrent != -1L))
            {
+        	   if (totalQuota == null) { totalQuota = 0L; }
                totalQuota += sizeCurrent;
            }
        }