I cannot submit a system program error since I don't know the default password

You set the password when you installed the OS. Use your password to not only log in but as authentication when using sudo (you will get no feedback, but type your password and hit ENTER)

The first user set up when you installed the system is an administrator. You need that password

If you have forgotten it then it can be reset see here

There are a few methods (mostly similar) take a look at these

http://www.psychocats.net/ubuntu/resetpassword

https://help.ubuntu.com/12.04/ubuntu-help/user-forgottenpassword.html

http://askubuntu.com/questions/24006/how-do-i-reset-a-lost-administrative-password

http://naveenubuntu.blogspot.co.uk/2012/05/recover-login-password-of-ubuntu-1204.html

I would like to clarify that I can log on to my desktop account i.e. I have not forgotten the password, however, I do not know the password for reporting this problem.

Bug reporting is done on Launchpad, and during the process of uploading bug information you are asked for your Launchpad login details.
You should be aware of these if you are able to ask questions on Launchpad.

There is no default password. You create a password when you install. The first user is automatically an administrator. If you are logged in as that user then that is the password to use.

Other users may or may not be administrators To check open a terminal (CTRL+ALT+T) and run the following command

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lsb_release -a; uname -a; id
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If this shows you are a member of the 'sudo' group you are and your password should be accepted

On my machine for example I see this

~$ lsb_release -a; uname -a; id
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.1 LTS
Release: 12.04
Codename: precise
Linux dell 3.2.0-32-generic-pae #51-Ubuntu SMP Wed Sep 26 21:54:23 UTC 2012 i686 i686 i386 GNU/Linux
uid=1000(warren) gid=1000(warren) groups=1000(warren),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),109(lpadmin),124(sambashare)

If you are not a member of the sudo group then you need to become one and you can do that by running

usermod -a -G sudo user

replacing user with your user name when logged in as root using a recovery console.

If you are a member of 'sudo' and your password is not being accepted then what program is asking for a password?