Connect to database hanging when using SmartGwt 4

Hi,
I am using a nightly build of SmartGwt 4. I noticed that when running the app in prod mode with a Tomcat backend it seems to hang when trying to connect to a mysql database when executing this statement

DriverManager.getConnection("jdbc:mysql://localhost:3306/", "userid", "password");

However this works fine when running in dev mode.

Also tried it with SmartGwt 3.1p nightly build and it works fine in both dev and prod modes.

Is there any config setting specific to SmartGwt 4.x that I might have missed?

Thanks.