Excel 2007 XmlMap.ExportXml producing empty string

[Clark Wilson]

(A colleague of mine is encountering a problem and I decided to post his
problem but I may not have gotten it quite right.)

If he manually exports from XML maps the export works. Programmatically
(from within an add-in developed using C#) it "succeeds" but produces an
empty string.

Until recently the programmatic way was working okay.

Excel 2007 SP1. At some past time was using VS 2005; now using VS 2008. Just
installed Forefront client (I mention this because I've seen posts about
certain XML functionality in some Microsoft contexts being affected by
permissions on temp folders, etc., etc.) He says the relevant PIA hasn't
changed in a long, long time.

Any ideas how to diagnose and fix this problem?

 

[Clark Wilson]

A tiny test add-in created from scratch in VS 2008 has the problem. A tiny
test add-in created from scratch in VS 2005 on the same machine does *not*
have the problem.

So we're on the way to a diagnosis and fix, I guess.