Just to throw in one more comment. In the dovecot.conf file it alsomentions that you should use the same separator between namespaces. Otherwise you might confuse the client.
I can confirm that Outlook Express and Thunderbird on windows seem largely unaffected even using *both* at the same time. I have been alternating back and forwards with no ill effects other than some folder subscription winges. You appear to need to close down and re-open each program sometimes to make it switch over
Ed W
