More of a feature than a bug -

If Idefine a new seam project as described in section 3.1.2 of the GSG at http://download.jboss.org/jbosstools/nightly-docs/en/GettingStartedGuide/html_single [ie. use the default settings + configure the database connection].
Then I repeat these steps using a new project name I find I cannot re-use the existing database connection.
I get a "Driver class property is empty for selected 'DefaultDS' connection profile" error in the New Seam Project window.

The only way I can find around this is to re-define the database connection to re-select the same database driver and re-enter the url as jdbc:hsqldb:hsql://localhost:1701 i.e all use the same values as before - nothing has changed.

The above feature is only evident if I test the connection whilst in the JDBC Connection properties page. If I don't test the connection I can define as many new seam projects as I like. So this is the workaround.