ToolkitScriptManager throws NullReferenceException during concurrent access to a page for the first time

Question

Hi everybody,

i'm developing a ASP.NET web application which uses the AjaxControlkit 3.0.30512.20315. I have a ToolkitScriptManager instance on my master page which has some ScriptReferences in the CombineScripts collection. If i access my default page from 2 differenct clients after an iisreset, i get the following exception

[NullReferenceException: Object Reference not set to an instance of an object.]
   System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) +143
   System.Collections.Generic.Dictionary`2.set_Item(TKey key, TValue value) +11
   AjaxControlToolkit.ToolkitScriptManager.GetScriptCombineAttributes(Assembly assembly) +129
   AjaxControlToolkit.ToolkitScriptManager.IsScriptCombinable(ScriptEntry scriptEntry) +148
   AjaxControlToolkit.ToolkitScriptManager.OnResolveScriptReference(ScriptReferenceEventArgs e) +415
   System.Web.UI.ScriptManager.RegisterScripts() +191
   System.Web.UI.ScriptManager.OnPagePreRenderComplete(Object sender, EventArgs e) +113
   System.Web.UI.Page.OnPreRenderComplete(EventArgs e) +8698462
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1029

Using .NET Reflector i found out that the GetScriptCombineAttributesmethod access a static dictionary, which is not protected against concurrent access. Either i have a race condition in my code or there is a bug in the AjaxToolkit.

Can anybody give me a hint on that one?

Thanks in advance