Just downloaded the latest DB Architect and trying to connect to my Postgres (v8.03) db and rev-eng back the ER diagrams.
Downloaded the latest Jdbc driver from postgres site 8.1-404.jdbc2.jar
Pointed the Jdbc IR options at the downloaded location and said Update. It processed the file and then get following error:
Instant Reverse unsuccessful.
Reason: Cannot found the jdbc driver class
I will report your finding to our engineers. At the moment, please try ORM reverse instead of Instant Reverse. They way to reverse database is by select Tools | Object Relational Mapping (ORM) | Reverse Database… from main menu. This way should work properly.