Just saw this on PalmGear... a maintenance release of DateBk4 v4.0d is now available. The Pimlico site hasn't been updated yet, however.

Update Description
Third maintenance release for DateBk4 includes fixes for virtually all reproducible issues with 4.0c. V-4.0d features improved beaming between all models and versions of the Palm OS and Palm OS devices, more options for undated ToDo's and a host of small refinements that users have asked for! Updated manual has also been posted.