nnimap, tick mark not synced when reading from 2 computers

[Par Kurlberg]

Work mail is kept on an exchange server, and I access it from two
computers (one laptop, the other my work desktop) using gnus+nnimap.
Recently (I think it is after I upgraded to emacs 24) I have had trouble
with tick marks not being synced properly.  E.g., when I untick a
message on my laptop, it is remains ticked in the summary buffer on my
desktop.  As far as I can tell, the %Flagged flag on the imap server is
being set/reset correctly from either client, but it seems like gnus
uses the information in ~/.newsrc.eld, and this overrides the flags on
the server.  (This suspicion could be wrong.)

Any hints on how to fix this?  (Or hints on how to debug it?)

Best,
Par 

PS: Some system info

Computer 1 (macos)

GNU Emacs 24.1.1 (x86_64-apple-darwin11.4.0, GTK+ Version 2.18.9) of
2012-06-20 on odin.local

Gnus v5.13


Computer 2 (ubuntu)

GNU Emacs 24.1.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.10) of 2012-06-21\
 
Gnus v5.13