"java.lang.NullPointerException"

Receiving this error when trying to hit third-party EMR application via HTTP; platform is Debian GNU/Linux, PostgreSQL is version 8.3, but have a previous instance of 8.2 on the machine that's not currently running. It has worked in the past for quite sometime, but I had to bounce the box and hop into single-user mode to reset root password, as we forgot it. As soon as I did that, and brought the server back up, this is the error we are all getting now.

What I've done to troubleshoot:

-Ensured that postgresql-8.3 and apache2 daemons were running via sysvconfig
-Ran this command under "postgres" user - "pg_ctl start -D /etc/postgresql/8.3/main -l postgres2011.log" (just created a new random log file, not sure if that was correct)
-Found what I believe are .jar files for current application, and tried to start "java -jar /absolute path of jar file" but received an error "Failed to load Main-Class manifest attribute"

I'm not even sure if I headed down the right path to begin with (I took this client over just a few weeks ago). This is simply a custom web app that has been written, and uses a PostgreSQL DB for the back end. Not too sure where to go from here, any help at all would be much appreciated, thank you much in advance.