Node number is lost when previewing the post before

I'm setting up a webSite using Drupal 7.2. However, when setting content type to force previewing (or even when previewing by ourself) the autoaliasing is kinda lost. In fact, the alias is really created, but the node number is lost. Hence, in the alias list I see something like:
"my/link/to/node/x" is linking to "node/"

I was suspecting the core previewing system of Drupal for this at first since all other settings were blank when previewing, but only pathauto seem to not work correctly. Here is some link to similar problems.

http://drupal.org/node/795256
http://drupal.org/node/323438
http://drupal.org/node/487358