Reference a node, save, and it disappears!

We've been experiencing a critical bug related to CCK nodereference (we're trying with the latest 6.x code). What happens is as follows:

1. Edit a node that contains a set of nodereferences in it.
2. Open a new tab and create a node to reference.
3. Go back to that node in Step 1 and reference the node from Step 2.
4. Save, but click Edit and notice the nodereference disappeared.

So, if you edit node A and create node B while node A is still open, the reference from node A->B disappears on save. However, if you create node B *before* node A is open for edit, and *then* open node A and reference node B, all is well on save. This is consistently reproducible in several environments.

We are using Drupal 6 CCK 3.0-alpha 3. We rolled back to 2.9, and it seems that issue is resolved but a related issue occurs -- and that is that when you click Add another item to add a new nodereference field, the entire nodereference area disappears. This latter issue seems to be more common with other people, but the former (main) issue doesn't seem to have any reports.

Has anyone experienced this? Can anyone help? We're trying to run traces using xDebug and the like, but we're otherwise stymied.

Thank you!