Update Manager won't work anymore

Looks like you modified your /etc/apt/source.list file and made a mistake. Edit the file, look at line 54 (where it says "usage") and fix it. Or just the entire file contents here.

i'm not sure how to edit the file, and now the message reads
E: Type 'usage:' is not known on line 49 in source list /etc/apt/sources.list
E: The list of sources could not be read.
Go to the repository dialog to correct the problem.
E: _cache->open() failed, please report.

i tried fixing it and got this
E: Type 'usage:' is not known on line 3 in source list /etc/apt/sources.list
E: The list of sources could not be read.
Go to the repository dialog to correct the problem.
E: _cache->open() failed, please report.

I beleive this is the file contents...when opened with gedit. is this what you need?

# deb cdrom:[Ubuntu 9.10 _Karmic Koala_ - Release i386 (20091028.5)]/ karmic main restricted
deb-src http://archive.ubuntu.com/ubuntu/ karmic main restricted #Added by software-properties
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://us.archive.ubuntu.com/ubuntu/ karmic restricted main
deb-src http://us.archive.ubuntu.com/ubuntu/ karmic restricted main multiverse universe #Added by software-properties

## Major bug fix updates produced after the final release of the
## distribution.
deb http://us.archive.ubuntu.com/ubuntu/ karmic-updates restricted main
deb-src http://us.archive.ubuntu.com/ubuntu/ karmic-updates restricted main multiverse universe #Added by software-properties

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ karmic universe
deb http://us.archive.ubuntu.com/ubuntu/ karmic-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://us.archive.ubuntu.com/ubuntu/ karmic multiverse
deb http://us.archive.ubuntu.com/ubuntu/ karmic-updates multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ karmic-backports restricted main multiverse universe
deb-src http://us.archive.ubuntu.com/ubuntu/ karmic-backports restricted main multiverse universe #Added by software-properties

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu karmic partner
deb-src http://archive.canonical.com/ubuntu karmic partner

deb http://security.ubuntu.com/ubuntu karmic-security restricted main
deb-src http://security.ubuntu.com/ubuntu karmic-security restricted main multiverse universe #Added by software-properties
deb http://security.ubuntu.com/ubuntu karmic-security universe
deb http://security.ubuntu.com/ubuntu karmic-security multiverse
usage: sudo [-n] -h | -K | -k | -L | -V | -v
usage: sudo -l[l] [-AnS] [-g groupname|#gid] [-U username] [-u username|#uid]
            [-g groupname|#gid] [command]
usage: sudo [-AbEHnPS] [-C fd] [-g groupname|#gid] [-p prompt] [-u
            username|#uid] [-g groupname|#gid] [VAR=value] [-i|-s] [<command>]
usage: sudo -e [-AnS] [-C fd] [-g groupname|#gid] [-p prompt] [-u
            username|#uid] file ...
usage: #gid] [-U username] [-u username|#uid]

   #gid] [command]

usage: #gid] [-p prompt] [-u

   #uid] [-g groupname|#gid] [VAR=value] [-i|-s] [<command>]

usage: #gid] [-p prompt] [-u

   #uid] file ...

Thanks Ryan Dwyer, that solved my question.