Just had a mail from the webhost - apparently they are moving the site(s) between servers tonight. It shouldn't affect availability of the sites - as they'll be mirrored on the new host while still being accessible on the old host - but it does affect whether or not people will be able to upload.

The short version is that while the domain name servers (dns) are propagating throughout the internet, people visiting the sites may be directed to the new site or they may be directed to the old site. After they've propagated (up to 24 hours), people will be directed only to the new site. ( Cut for technical information, if you're interested )

Because the new site is just a copy of the old, that won't matter for content already there. So you will still be able to read the stories. However, if you are still being directed by your ISP to the old site, because the ISP has not updated their dns information, and you upload or edit your stories, you'll actually be posting to the site on the old server and those changes will not appear on the new site. The old site will eventually disappear from the internet, and with it your new stories or edits.

I've already updated the front page of the site with this information, asking people not to post new or edit existing stories until Thursday (by which time the dns should have propagated).