Why does IE5 give me a "No suitable driver" error?

I am using PostgreSQL 7.0.2 JDBC, applet works fine with Netscape, but
IE5 gives me a "java.sql.SQLException: No suitable driver" error.

I am using the following mechanism:

Class.forName("org.postgresql.Driver");
db = DriverManager.getConnection("jdbc:postgresql://www.....

What am I doing wrong?
Charles