'Invalid character' client errors

[dahlbyk]

I can't reproduce on any of my machines (of course), but our production JS error reporting shows a bunch like this, for a variety of browsers:

UncaughtException: Invalid character
    at http://example.com/cassette.axd/script/8fa1005870134091d6c3a11981ce9daafdb0dfa1/content/js/whatever.js:1

Similar errors include:

• UncaughtException: SyntaxError: Invalid character '\u0031'
• UncaughtException: SyntaxError: illegal character

What's interesting is that I haven't seen this error for any of the bundled scripts, only for individual scripts configured like so:

    public class CassetteBundleConfiguration : IConfiguration<BundleCollection>
    {
        private const string jsBase = "content/js/";
        private const string cssBase = "content/css/";

        private static readonly FileSearch fileSearch = new FileSearch
        {
            SearchOption = SearchOption.AllDirectories,
        };

        public void Configure(BundleCollection bundles)
        {
            bundles.AddPerIndividualFile<StylesheetBundle>(cssBase, fileSearch);
            bundles.AddPerIndividualFile<ScriptBundle>(jsBase, fileSearch);

            // init bundles...
        }
    }

    public static class AppHelper
    {
        public static string JsUrl(string jsFile)
        {
            return Bundles.Url<ScriptBundle>("/content/js/" + jsFile);
        }
    }

The scripts are pulled into the view with:

<script type="text/javascript" src="<%= AppHelper.JsUrl("whatever.js") %>"></script>">

Has anyone seen this?

[dahlbyk]

Worth a thousand words: