I've been able to troubleshoot the issue further.
I had been manually formatting my code snippets in previous posts but with my latest post I decided I would try to get the CodeFormatter extension working. It worked fine with this syntax:
[code:c#;ln=on;alt=on]<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE8">[/code]
When I include that snippet in my post though, the syndication breaks and I get the "Unable to cast object of type 'BlogEngine.Core.Web.HttpHandlers.SyndicationHandler' to type 'System.Web.UI.Page'" error message.
I was able to temporarily fix it just by removing the [code] command. I would like to get it working though.
Anyone have any clue what is causing this?