I have 2 blogs with the exact same plugins, on the same host/server. Both use the same Apache, the same PHP, the same core WordPress 2.8.4 files. Both use the same permalinks, and are installed in a subdirectory 'wordpress' with the appropriate settings. Both use the same .htaccess settings.
Blog 1 - can preview Draft posts, works as expected.
Blog 2 - triggers a 404 error when trying to preview a Draft post.
Any suggestions on what could be different enough to get a 404 on Blog 2 while the same thing works fine on Blog 1?