I have installed git on my 64-bit 12.04.2 Ubuntu. But when I try to clone it gives me the error:

#git clone git://git.kernel.org/pub/scm/git/git.git
Cloning into 'git'...
This is nc from the netcat-openbsd package. An alternative nc is available
in the netcat-traditional package.
usage: nc [-46DdhklnrStUuvzC] [-i interval] [-P proxy_username] [-p source_port]
[-s source_ip_address] [-T ToS] [-w timeout] [-X proxy_protocol]
[-x proxy_address[ort]] [hostname] [port[s]]
fatal: The remote end hung up unexpectedly

But when I give the command:
#git clone http://git.kernel.org/pub/scm/git/git.git
the operation is successful, any clues what I may be doing wrong?

Hi,

Make sure your firewall isn't blocking port 9418.

Cheers

Using ftp_proxy as ftp_proxy=ftp:// was causing the issue, but using ftp_proxy=http:// worked. Any idea Why?

Sounds like you got a firewall that is blocking a lot of outgoing ports with http as one of the exceptions.

Cheers