After talking about Kerberos kernel authentication earlier I noticed that there was a hotfix available for a crash related to the feature. Kernel mode authentication is a new feature in IIS7 that optimizes the authentication of connections. This particular crash occurs when using a custom domain account for the application pool credentials. I don't know of anyone who has seen this crash in connection with a WCF service but the symptoms are a stop code of 7E and a call stack that includes HTTP!UlpThreadPoolWorker. Similar to the other article, you've got a choice between using the classic user mode authentication or applying the fix to continue using kernel mode authentication.