Vista - DotNet program opens shadow datafile rather than the current one

I'm having (what seems to me) like a really strange problem with Vista
Business.

I install an app (my own) from an MSI that has a program file (dotnet
2) and a configuration file (the configuration is stored in an access
database). So far so good, I install it on Vista and everything works
fine.

Then I install an upgrade. The upgrade writes in a revised copy of the
configuration file and a new program and when I look at it it has
installed correctly and I can see the shadow copy hiding behind the
configuration file on the properties menu.

Then I run my new program, AND IT OPENS THE SHADOW COPY not the
current one. I even tried telling my program to copy the file from
within the .Net framework and open the copy, but no dice, it copies
the shadow not the current copy! Bizarre behaviour, or what?

What is all that about? Is this just a bug in Vista? Looking around
google I can see a couple of other people reporting strange collisions
between access databases and vista's shadowing mechanism. But no
solutions apart from one person who thought that rebooting would make
the problem go away; it doesn't in my case.

Tom