I am using activ sync + TB 1.5.0.12 with Win Mob 2003 and just registered Birdie. After this, i no longer manage to sync. ActivSync reports many unresolved items. I then deleted the connection and synced again. The results was that all items on my mobile are deleted. ActivSync confirms that there are many unsynced items, which indeed are all my contact and all the events on my computer!
After analyzis, it appears that the versions of BirdieSync on the mobile and on the desktop didn't match causing some problems.
An alert was added in 1.5.4.4 to signal the difference of versions.