problem to connect to database

Hi all!

I really need your help for this. I installed the JDBC driver on my
machine by copying the jar file in C:\Program Files\Apache Software
Foundation\Tomcat 5.0\common\lib\pg73jdbc3.jar and set environment
variable CLASSPATH to this path. I create a JSP page (code below).
The first time I launched this JSP page, all was ok. I don't use it
since last week but when I try to launched it yesterday, I got an error
to connecting database :

Error establishing the connection :
Something unusual has occured to cause the driver to fail.
Please report this exception: Exception: {0}

So, I don't think the error come from my code because it already work with the same code but I don't know what I do to cause this error now.
Any help will be greatly appreciated.

Melanie

-------code for jsp page---------
<%
/* Load the JDBC Driver */
try {
Class.forName("org.postgresql.Driver");
}catch(ClassNotFoundException cnfe) {
out.println("<BR>Error loading driver " + cnfe + "<BR>");
}
/* Define the connection URL */
String dbName = "gec_test";
String host = "localhost";
String postgresqlUrl = "jdbc:postgresql://" + host + "/" + dbName;
/* Establish the connection */
String username = "bergeron.melanie";
String password = "*****";
try{
Connection connection = DriverManager.getConnection(postgresqlUrl,
username, password);
...
}
connection.close();
}catch(SQLException e){
out.println("<BR>Error establishing the connection : " + e + "<BR>");
}