We always assumed wherever you have an HTTP Context (i.e., wherever SPContext.Current is not null), that you could access the SharePoint context through SPContext.Current. This was the case with MOSS 2007 RTM and SP1, but this changed with the recent Infrastructure Update. The following update to when SPContext is supported has been confirmed by Microsoft PSS. (Props to Nishand for confirming this behavior change.) Prior to the IHttpHandler.ProcessRequest method, the SharePoint application runtime...(read more)