SSRS 2008 R2 not calling my custom assembly code but also not giving me an error?

We have several reports (not authored by me) that call a C# custom assembly that has 1 method.  The 1 method converts an html input string into a bitmap and return the bitmap.  The 1 method's call signature looks like this:

public byte[] GetImage(string html)

The existing reports run without error, and they convert html to images, but we weren't happy with the conversion results.  Sooo I was tasked with creating a new custom assembly that uses the same call signature - but uses Aspose.Words to do the image conversion.

To that end I coded a new custom assembly with  a GetImage method.  I registered both my custom assembly and Aspose in the gac on the DB server and in the report .rdl I updated the CodeModule declarations to use Aspose and my new assembly:

  <CodeModules>
    <CodeModule>Aspose.Words, Version=9.5.0.0, Culture=neutral, PublicKeyToken=716fcc553a201e56</CodeModule>
    <CodeModule>SSRSCustomTables, Version=1.0.0.0, Culture=neutral, PublicKeyToken=583b5b1f13c0ee82</CodeModule>
  </CodeModules>
  <Classes>
    <Class>
      <ClassName>CustomAssembly.GetImageClass</ClassName>
      <InstanceName>ImgClass</InstanceName>
    </Class>
  </Classes>

The existing reports all call the image conversion method like this:

                              <TablixCell>
                                <CellContents>
                                  <Image Name="Image3">
                                    <Source>Database</Source>
                                    <Value>=IIF(Fields!SpecificationDescription.Value is system.DBNull.value,"stop",IIF(Fields!SpecificationDescription.Value = "","stop",Code.ImgClass.GetImage(Fields!SpecificationDescription.Value)))</Value>
                                    <MIMEType>image/bmp</MIMEType>
                                    <Style>
                                      <Border>
                                        <Style>None</Style>
                                      </Border>
                                    </Style>
                                  </Image>
                                </CellContents>
                              </TablixCell>

The report uploads and runs without error -but- when I preview it I see the "white box with a red X missing image" placeholder where the images should appear.  The custom assembly functions correctly in a small testbed app that feeds the GetImage method some html but it doesn't work in the report.

I put a SQL Profiler trace on the server looking for TSQL and AssemblyLoads.  Then I started the reporting server and ran a report.  The trace showed the correct sql statements were executing but it never fired an event for an assembly load even though I had the trace running before I started the reporting server instance.

Questions:

• Does anybody have any thoughts on what might be happening - it seems to me that the GetImage method is never being called but I don't get any errors
• When should the "assembly load" profiler events fire - I didn't get any events and I had profiler running before I started the reporting server
• If the "assembly load" events fire when the database engine is started is there any way to trace an engine start?

--Richard