Unable to install anything on ubuntu 13.04 Raring Ringtail

Unable to install anything on ubuntu 13.04 Raring Ringtail

A few days back, I was on a stable Ubuntu 13.04 install that i messed up
while trying different Dekstop environments, and thus, i totally screwed
it up after trying to get a ful Gnome3 experience. As a result, The
right-click context menu stopped wrking in Unity, would freeze when i
minimize any window, + all the fonts were messed up, so i decided to go
for a clean re-install.
I did. After which, im unable to install anything on it. I first recieved
errors while installing Chrome or SKype, but considering it to be
perfectly normal, I mannually installed the missing Libraries and
succeeded installling chrome.
But nothing else installs. If i try installing something through the
Terminal, i get stupied errors like: E: Unable to locate package leafpad
or: Package synaptic is not available, but is referred to by another
package. This may mean that the package is missing, has been obsoleted, or
is only available from another source
or: E: Package 'synaptic' has no installation candidate.
IF i use the Software center i get this error:
http://www.flickr.com/photos/96009096@N06/9534183933/
or if the package is from the UNIVERSE or MULTIVERSE sources and i click
on 'USE THIS SOURCE' button, It starts some "updating cache" process that
fails after sometime, with a stupid message saying: "FAILEED TO UPDATE
REPOSITORY INFORMATION please check your internet connection and try
again." http://www.flickr.com/photos/96009096@N06/9536970330/
Please help me out of this.. I'm not exactly a complete newbie to Linux,
and have been using Ubuntu for ages, but never was much good at handling
errors, and this is a situation where i just am not 'allowed' to do
anything seeing as i get stupid errors every time i try installling
something. and thus for some reason or another, EVERY install fails...