Moving to a new forum technology is a huge job. Thanks to Tom's hard work over many long nights, we've managed to port all the users and posts from the old phpBB forum to this new WebWiz forum running on ASP. (They're two totally different technologies so this is actually pretty impressive!) Quite often using a new forum technology means just wiping everything - everyone would have to sign up again, and the forum would be back to zero posts! However, Tom's managed to transfer the meat of it.
There are a few formatting issues with transferred posts, and PMs and post attachments haven't made it. Due to the great technical complexity of converting the databases, it might be difficult to fully resolve this. Tom's still working on it though, and hopefully will be able to come up with something. It might need a compromise, though.
In the meantime, the old forum is still online in read-only mode here:
The old Scirra phpBB forum
If you want to manually access or copy across any PMs or files, you can find them there. (Note this forum is using a separate database, so if you changed your password on the new site, the account on the old forum will still be using your old password.)
Hopefully this is a good enough compromise for the time being, and as always, we're working on it :)