Synchronizing Outlook 2010 on desktop and laptop

[ChrisW]

When I go away I have been in the habit of copying my Outlook.pst file
from the desktop to the laptop and then back again on my return. Only
one computer is in use at any one time. This has worked well for me
for many years and I have never lost a message. Since upgrading to
Outlook 2010 I have had problems. Both the desktop and laptop have
Outlook 2010 installed with the same accounts and profile and
idnetical settings except on the laptop I have Outlook set to Download
Headers only for messages larger than 100Kb, leaving the message on
the server. This is because I can often only get dialup speeds on my
laptop's mobile internet link.

When the message is larger than 100Kb it always shows twice on the
laptop. I don't know why but it has never been a problem. Usually
when I get home I synchronize the .pst files and on my desktop the
full message is then downloaded. Since installing Outlook 2010 I get
a message telling me that "Some of the selected headers were
downloaded from an E-mail account that doesn't exist on this computer"
It gives me two options - to keep or remove the headers. I select
"keep". The message body does not get downloaded on to the PC but it
does immediately get deleted from the (web) server so I end up with
just the headers and not the message body.

What has changed in Outlook 2010 to make this happen? I am confused
as I have changed nothing in the way I operate the programme.

I have never felt the need of using a commercial synchronization
programme. There must be many people who, like me, want to use just
one .pst file on more than one computer but only on one at a time. Is
there a better way than just synchronizing the .pst files or does
Outlook 2010 require files other than the .pst file to be synchronized
as well?