Workaround for Cassette precompiledManifest issue with application cirtual path: https://groups.google.com/forum/?fromgroups#!topic/cassette/pNIxVczsHEg

woraround.cs

using System;
using System.Web;
using System.Text.RegularExpressions;
using System.Xml.Linq;

public static class CassetteHelper
{
    private static readonly Regex EnsurePathRegex = new Regex(@"((?:href|src)\s*=\s*"")/(_cassette/)",
                                                              RegexOptions.Compiled);

    public static string EnsureVirtualPath(string html, string virtualPath)
    {
        return EnsurePathRegex.Replace(html, m => String.Concat(m.Groups[1].Value, virtualPath, m.Groups[2].Value));
    }

    internal static void FixCassetteXmlFile(HttpServerUtility server)
    {
        try
        {
            string xmlFile = server.MapPath("~/App_Data/cassette.xml");
            string virtualPath = HttpRuntime.AppDomainAppVirtualPath;
            if (String.IsNullOrEmpty(virtualPath) || virtualPath.Equals("/"))
                return;
            if (!virtualPath.EndsWith("/"))
                virtualPath += "/";

            XDocument doc = XDocument.Load(xmlFile);
            if (doc.Root == null)
                return;
            var htmlElements = doc.Root.Descendants("Html");
            foreach (var htmlElement in htmlElements)
            {
                htmlElement.Value = EnsureVirtualPath(htmlElement.Value, virtualPath);
            }
            doc.Save(xmlFile);
        }
        catch
        {
            //don't really care, but don't fail application start.
        }
    }
}