User pictures/avatars broken?

I've been tracking Drupal CVS on a site I'm developing, and recently (the last two or three days, I think) user avatars/pictures aren't being displayed. They're uploading okay (I have downloads set to "private", with a path outside the web root). Nothing is being inserted in the "picture" block of my theme.

I've tried a clean install of Drupal CVS from today (using my current database) with an untouched xtemplate and they're still not working.

theme('user_picture', $node) returns nothing in xtemplate_node()

The "picture" field in the user table contains the absolute path to the uploaded image.

The "xtemplate_picture_*" vars in the database are set to 1.

If anybody else has this problem please drop a follow-up to this. If it's just me I'll try to fix it myself, otherwise I can wait for a fix in CVS.