diff --git a/src/Umbraco.Core/IDisposeOnRequestEnd.cs b/src/Umbraco.Core/IDisposeOnRequestEnd.cs
new file mode 100644
index 0000000000..cf1ec3a177
--- /dev/null
+++ b/src/Umbraco.Core/IDisposeOnRequestEnd.cs
@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Umbraco.Core
+{
+    /// <summary>
+    /// Any class implementing this interface that is added to the httpcontext.items keys or values will be disposed of at the end of the request.
+    /// </summary>
+    public interface IDisposeOnRequestEnd : IDisposable
+    {
+    }
+}
diff --git a/src/Umbraco.Core/Models/UmbracoObjectTypesExtensions.cs b/src/Umbraco.Core/Models/UmbracoObjectTypesExtensions.cs
index a97f1fe976..7cc130600b 100644
--- a/src/Umbraco.Core/Models/UmbracoObjectTypesExtensions.cs
+++ b/src/Umbraco.Core/Models/UmbracoObjectTypesExtensions.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using Umbraco.Core.CodeAnnotations;
 
@@ -9,7 +10,8 @@ namespace Umbraco.Core.Models
     /// </summary>
     public static class UmbracoObjectTypesExtensions
     {
-        private static readonly Dictionary<UmbracoObjectTypes, Guid> UmbracoObjectTypeCache = new Dictionary<UmbracoObjectTypes,Guid>();
+        //MUST be concurrent to avoid thread collisions!
+        private static readonly ConcurrentDictionary<UmbracoObjectTypes, Guid> UmbracoObjectTypeCache = new ConcurrentDictionary<UmbracoObjectTypes, Guid>();
 
         /// <summary>
         /// Get an UmbracoObjectTypes value from it's name
@@ -48,24 +50,22 @@ namespace Umbraco.Core.Models
         /// <returns>a GUID value of the UmbracoObjectTypes</returns>
         public static Guid GetGuid(this UmbracoObjectTypes umbracoObjectType)
         {
-            if (UmbracoObjectTypeCache.ContainsKey(umbracoObjectType))
-                return UmbracoObjectTypeCache[umbracoObjectType];
+            return UmbracoObjectTypeCache.GetOrAdd(umbracoObjectType, types =>
+                {
+                    var type = typeof(UmbracoObjectTypes);
+                    var memInfo = type.GetMember(umbracoObjectType.ToString());
+                    var attributes = memInfo[0].GetCustomAttributes(typeof(UmbracoObjectTypeAttribute),
+                        false);
 
-            var type = typeof(UmbracoObjectTypes);
-            var memInfo = type.GetMember(umbracoObjectType.ToString());
-            var attributes = memInfo[0].GetCustomAttributes(typeof(UmbracoObjectTypeAttribute),
-                false);
+                    if (attributes.Length == 0)
+                        return Guid.Empty;
 
-            if (attributes.Length == 0)
-                return Guid.Empty;
+                    var attribute = ((UmbracoObjectTypeAttribute)attributes[0]);
+                    if (attribute == null)
+                        return Guid.Empty;
 
-            var attribute = ((UmbracoObjectTypeAttribute)attributes[0]);
-            if (attribute == null)
-                return Guid.Empty;
-
-            UmbracoObjectTypeCache.Add(umbracoObjectType, attribute.ObjectId);
-
-            return attribute.ObjectId;
+                    return attribute.ObjectId;
+                });
         }
 
         /// <summary>
diff --git a/src/Umbraco.Core/Persistence/UmbracoDatabase.cs b/src/Umbraco.Core/Persistence/UmbracoDatabase.cs
index 522e0b4173..98d5d9cebc 100644
--- a/src/Umbraco.Core/Persistence/UmbracoDatabase.cs
+++ b/src/Umbraco.Core/Persistence/UmbracoDatabase.cs
@@ -16,7 +16,7 @@ namespace Umbraco.Core.Persistence
 	/// can then override any additional execution (such as additional loggging, functionality, etc...) that we need to without breaking compatibility since we'll always be exposing
 	/// this object instead of the base PetaPoco database object.	
 	/// </remarks>
-	public class UmbracoDatabase : Database
+    public class UmbracoDatabase : Database, IDisposeOnRequestEnd
 	{
         private readonly Guid _instanceId = Guid.NewGuid();
 		/// <summary>
diff --git a/src/Umbraco.Core/Umbraco.Core.csproj b/src/Umbraco.Core/Umbraco.Core.csproj
index 2cc6a8fbd4..dc95d29ab4 100644
--- a/src/Umbraco.Core/Umbraco.Core.csproj
+++ b/src/Umbraco.Core/Umbraco.Core.csproj
@@ -166,6 +166,7 @@
     <Compile Include="Events\SaveEventArgs.cs" />
     <Compile Include="Events\SendToPublishEventArgs.cs" />
     <Compile Include="IApplicationEventHandler.cs" />
+    <Compile Include="IDisposeOnRequestEnd.cs" />
     <Compile Include="IO\ResizedImage.cs" />
     <Compile Include="IO\UmbracoMediaFile.cs" />
     <Compile Include="Media\MediaSubfolderCounter.cs" />
diff --git a/src/Umbraco.Web/UmbracoContext.cs b/src/Umbraco.Web/UmbracoContext.cs
index 17751b4077..2458dc62e0 100644
--- a/src/Umbraco.Web/UmbracoContext.cs
+++ b/src/Umbraco.Web/UmbracoContext.cs
@@ -24,7 +24,7 @@ namespace Umbraco.Web
     /// <summary>
     /// Class that encapsulates Umbraco information of a specific HTTP request
     /// </summary>
-    public class UmbracoContext : DisposableObject
+    public class UmbracoContext : DisposableObject, IDisposeOnRequestEnd
     {
         private const string HttpContextItemName = "Umbraco.Web.UmbracoContext";
         private static readonly object Locker = new object();
diff --git a/src/Umbraco.Web/UmbracoModule.cs b/src/Umbraco.Web/UmbracoModule.cs
index 79f029c4a7..5ba568c56e 100644
--- a/src/Umbraco.Web/UmbracoModule.cs
+++ b/src/Umbraco.Web/UmbracoModule.cs
@@ -467,11 +467,15 @@ namespace Umbraco.Web
         /// <param name="http"></param>
         private static void DisposeHttpContextItems(HttpContext http)
         {
+            // do not process if client-side request
+            if (http.Request.Url.IsClientSideRequest())
+                return;
+
             //get a list of keys to dispose
             var keys = new HashSet<object>();            
             foreach (DictionaryEntry i in http.Items)
             {
-                if (i.Value is IDisposable || i.Key is IDisposable)
+                if (i.Value is IDisposeOnRequestEnd || i.Key is IDisposeOnRequestEnd)
                 {
                     keys.Add(i.Key);
                 }