In Umbraco 4.5.2 I suddenly experience problems when using gzip-compression on the page content. When turning compression on using fairly standard code, on the client side (whatever browser) I get "invalid content encoding" errors, which was not a problem before. I traced the problem back to the Client Dependency Module, but did not arrive at a solution.

On the page_load() of a .master page (or any other .aspx page for that matter) I force gzip compression with fairly standard code:

 
        HttpResponse Response = HttpContext.Current.Response;
        Response.Clear();
        Response.Filter = new System.IO.Compression.GZipStream(Response.Filter, System.IO.Compression.CompressionMode.Compress);
        Response.AppendHeader("Content-Encoding", "gzip"); 

In Umbraco 4.0.2 this works without problems, but in Umbraco 4.5.2 results in "invalid content encoding" errors. The result won't even show in Firebug. Inspection of the HTTP stream in WireShark shows decoding errors, and the gzip encoded data seems to be present multiple times, each repetition being incomplete, so garbage actually. Really odd.

After some intensive research I can only conclude it must have something to do with the new Client Dependency Module. When in web.config I comment out the <modules> section entry  <add name="ClientDependencyModule" type="ClientDependency.Core.Module.ClientDependencyModule, ClientDependency.Core" /> the compression works normally as before, and the gzipped page is decoded and shown correctly. But when I again uncomment it I get the same rubbish.

I tested this in both IIS6 and 7 on different machines, and on the client side with different browsers, with the same problematic result. As far as I can see is not caused by IIS configuration settings. The compression problem seems to be linked to the combination of Umbraco 4.5.2 and its Client Dependency Module.

I'd really like to continue using page content compression. Anyone got an idea?