merge fails "file in use"

[Snidely]

I'm using Tortoise HG 1.1.1 (Mercurial-1.6.1023) and one of the files
I am trying to deal with is an Open Office document (.odt).   When I
try to merge, from either the command line (W7 command.exe) or via the
THG "explore repository" shell extension, it fails because it wants OO
to open the document, but then complains "cannot access the file
because it is in use by another process: document.odt.orig"

For this particular merge, I'd like to keep the CWD version of
document.odt, and so I can just reject all the changes, but that
doesn't prevent the abort.   Selecting "internal:fail" for the merge
tool in the THG dialog doesn't change this behaviour (aka Error 32).

What should I be doing to get past this?   Thanks for your help!

/dps