Make sure you are using the latest editions of BOTH PC and Palm Companion products. 1.7.50 for the PC side of the house and 1.0.3 for the Palm Companion. This error is indicative of one side not being up to date with the latest.
In reading this message closer, I'm sorry for the confusion, but your PC side is what's not up-to-date. Have you opened and run your logbook on the PC side and let the database structure update itself? If you have in fact run Logbook Pro on the PC side, not just installed 1.7.50, then please create a backup (File..Archive..Backup) and e-mail it to email@example.com and I'll ensure the structure gets the 1.7.50 update that it seems yours didn't get.