The roaming causes each PC to take a copy of the "C:\Documents and
Settings\<user>\Application Data\gnupg" directory at login. If 2 PC's login
simultaneously, they'll each get a COPY. They can then make separate changes,
but don't see updates made by the other user. When they logout, their changes
are uploaded back to the Profile server. The last person to logout overwrites
the changes made by the 1st user to logout.

The problem for me is that I'm using a Windows Roaming profile. That means I'm
using a COPY of my profile on 2 separate machines. Any changes on one machine
are not detected by the other. On logout, any changes are synched backl to the
Profile Server.
To get round this, I need to stop using the Windows Profile area to store keys.
I stumbled on this...
http://lists.gnupg.org/pipermail/gnupg-users/2008-April/033224.html
...and set my gpg.conf to the following...

Thanks Moritz. I'm happy to try this out, but I'd need a binary if possible...

Thanks for the info. This may be related to:
T1008
...where GnuPG2 doesn't get installed sometimes.