Hello, I have using windows until now, so i'm totaly Linux beginner
I have downloaded Ubuntu 12.10 beta and successfully installed it on my pc.
Problem is because I cant install any software from software center and do update, it shows this message:

Failed to download repository information

Check your Internet connection.

Details

W:GPG error: http://packages.medibuntu.org quantal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2EBC26B60C5A2783, W:Failed to fetch bzip2:/var/lib/apt/lists/partial/rs.archive.ubuntu.com_ubuntu_dists_quantal_main_so urce_Sources Hash Sum mismatch
, W:Failed to fetch bzip2:/var/lib/apt/lists/partial/rs.archive.ubuntu.com_ubuntu_dists_quantal_univers e_source_Sources Hash Sum mismatch
, W:Failed to fetch bzip2:/var/lib/apt/lists/partial/rs.archive.ubuntu.com_ubuntu_dists_quantal_main_bi nary-i386_Packages Hash Sum mismatch
, W:Failed to fetch bzip2:/var/lib/apt/lists/partial/rs.archive.ubuntu.com_ubuntu_dists_quantal_univers e_binary-i386_Packages Hash Sum mismatch
, E:Some index files failed to download. They have been ignored, or old ones used instead.
It's problem whit internet connection, it work fine with wireless connection.
Can somebody help me?
Thanks in advance