SharePoint Workflow Not Starting from code (WorkflowManager)

Hi experts,

I am experiencing weird issue. Sometimes my workflows run, sometimes they don't.

I have built a SPD reusable workflow for a content type. 

I then created a list, and add this workflow to my list. 

There is an ItemAdded receiver with the following code:

                Guid siteID, webID, listID;
                int itemID;
                listID = properties.ListId;
                itemID = properties.ListItem.ID;
                using (SPWeb web = properties.OpenWeb())
                {
                    siteID = web.Site.ID;
                    webID = web.ID;
                }

                //Use elevated permission
                SPSecurity.RunWithElevatedPrivileges(delegate()
                {
                    using (SPSite site = new SPSite(siteID))
                    {
                        using (SPWeb web = site.OpenWeb(webID))
                        {
                            web.AllowUnsafeUpdates = true;
                            SPListItem item = web.Lists[listID].GetItemById(itemID);
                            if (item != null)
                            {
                                StartWorkflow(item, contentTypeName, workflowName);
                            }

                            web.AllowUnsafeUpdates = false;
                        }
                    }
                });


        private static void StartWorkflow(SPListItem listItem, string contentTypeName, string workflowName)
        {
            SPWorkflowAssociation wfAssoc = listItem.ContentType.WorkflowAssociations.GetAssociationByName(workflowName, System.Globalization.CultureInfo.CurrentCulture);
            listItem.Web.Site.WorkflowManager.StartWorkflow(listItem, wfAssoc, wfAssoc.AssociationData, true);
            listItem.Update();
        }

When I debug it, my receiver is called every time a new item is created. However, sometimes the StartWorkflow line throws error 

An exception of type 'Microsoft.SharePoint.SPException' occurred in Microsoft.SharePoint.dll but was not handled in user code

FAILED hr detected (hr = 0x8102008a)

in the log : COMException: <nativehr>0x8102008a</nativehr>

I tried the recommended solution from this article :
http://social.technet.microsoft.com/forums/sharepoint/en-US/53db57ac-c4b5-448e-9b2d-c8e17b8055df/workflow-intermittently-does-not-start

but it doesn't help.

Any ideas?

Thanks,

Andreas