Excel 32bit using 64bit addin

I'm running Excel 2007 32bit under Windows 7 64bit and I've developed an Excel addin that has a custom task pane and 2 command bar buttons. The task pane loads some information from a few XML files using MSXML. The addin in written in C# and it uses another native 开发者_如何转开发COM component that loads the XML.

When debugging I had set the active config in VS2010 to Debug|Win32 thinking that 32bit office can only use 32bit addins. The context menu would display ok but when it came to loading the XML I would get an "Unable to load Typelibrary" error at ISAXXMLReader::parseURL. The confusing part is to successfully load the XML I had to set the active config to Debug|x64.

Is there something I'm missing? Shouldn't 32bit Excel only be able to load 32bit addins?

N.B. In VS solution Win32 and x64 platform .NET code target is Any CPU and then native code target is x86/x64 respectively.

32 bit Excel should not be able to run to run a 64 bit addin. It sounds like there might be mis-match somewhere in your solution configurations. Perhaps a screen-shot of Configuration Manager could help diagnose the issue.