With a new server in place & nearly set up it will soon be time to move the forum files over.
This will inevitably mean freezing the forums for however long it takes - just did a quick check - 600MB & 139,000 files on the forums & that doesn't include the images ... it may take some time & I may have to drop old images again - so old avatars may be exterminated!
The rest of the site SHOULD transfer seamlessly - in other words the main site users will not even know anything has happened .. - if I've got things right .... but the forums will have to be put on hold during their transfer - I can't see any other way. Because they are live & in constant use any input during work causes major troubles.