Some users on OSX 10.6 may have encountered a blank Plant Database in Vectorworks:
This issue is caused by older versions of fonts in Font Book, usually duplicates of newer fonts, remaining after an OS update. (10.4 to 10.6 and/or 10.5 to 10.6) If you go to Applications > Font Book, you will see some fonts may have yellow warnings next to them, explaining that duplicates have been found.
To correct this, either remove the old font (if two are listed) or go to Edit > Resolve Duplicates in Font Book for any fonts with the yellow warning icon, then restarting the machine.