New to linux based OS, mythbuntu

ok so basically i think i've done good figuring most things out, but i've got Mythbuntu on my HTPC (that i'm on atm) and i can't install anything off of Ubuntu Software Center. It keeps telling me to check my internet connection, which seeing as i'm posting this is obviously connected. I can't get wine which is annoying but the worse thing is i can't get flash installed... can i use the terminal to bypass USC? and if so what do i put in the terminal to get these 2 programs to install?

it's not just Ubuntu Software Center, it's anything i want to download. tried running updates today (i have 130 updates to dl) and i get this error: "The action would require the installation of packages from not authenticated sources." do i have something set up wrong? i could really use help on this, I'm completely new to Linux and while there are a lot of things i like, this one thing if i can't fix it is going to ruin it completely for me. This is for an HTPC, so i HAVE to be able to download and install certain programs.

i did all that, i ended up figuring it out after messing with some things, incase anyone has the same problem go to the Update Manager > Settings (bottom lefthand corner) > Ubuntu Software and check ."Software Restricted by Copyright or Legal Issue" and "Source Code" then go to Other Software tab and make sure everything is checked. i messed around with a bunch of other stuff, but i believe this is what did it... i also clicked "Download From:" and "Other..." and hit ".Choose best" and it changed where i downloaded from.

lol ypu, closed... and yeah i'm learning terminal is a lot quicker once you start to learn it, a lot simpler too.