Here is some more detail on that error. I cleaned out the system log, and reran the post operation. The following error seems to be the main issue.
2009-09-21 19:04:35,989 ERROR mojoPortal.Web.Global - 71.234.245.71-en-US - /HtmlEdit.aspx?mid=11&pageid=5
System.InvalidOperationException: Unable to generate a temporary class (result=1).
error CS2001: Source file 'C:\WINDOWS\TEMP\4bjqhj7a.0.cs' could not be found
error CS2008: No inputs specified
at System.Xml.Serialization.Compiler.Compile(Assembly parent, String ns, XmlSerializerCompilerParameters xmlParameters, Evidence evidence)
at System.Xml.Serialization.TempAssembly.GenerateAssembly(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, Evidence evidence, XmlSerializerCompilerParameters parameters, Assembly assembly, Hashtable assemblies)
at System.Xml.Serialization.TempAssembly..ctor(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, String location, Evidence evidence)
at System.Xml.Serialization.XmlSerializer.GenerateTempAssembly(XmlMapping xmlMapping, Type type, String defaultNamespace)
at System.Xml.Serialization.XmlSerializer..ctor(Type type, String defaultNamespace)
at System.Xml.Serialization.XmlSerializer..ctor(Type type)
at mojoPortal.Business.SerializationHelper.SerializeToString(Object obj)
at mojoPortal.Business.WebHelpers.IndexWriterTask.QueueTask()
at mojoPortal.Web.SiteUtils.QueueIndexing()
at mojoPortal.Web.ContentUI.EditHtml.SaveHtml(Boolean draft)
at mojoPortal.Web.ContentUI.EditHtml.btnUpdate_Click(Object sender, EventArgs e)
at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)