have you added the PPA to your source list as well
I wish I could, I use Unbuntu as well, been having problems for a while now, I currently have to reinstall it on a daily basis, it's driving me nuts!!!
I can't reinstall chrome or skype even if I try and do it from the ubuntu soft ware centre! Are you trying to install it from there software center? Or from else where, I know ubuntu doesn't support all applications, it may not be possible to have it.
are you using AMD64 or 1386 , one is 64 bit the other is 32 bit that may be your problem .
linux recommend 32 bit for most users as most software works straight out of box on it , i use 64 bit and it can be a hassle at times as some software wont work on it . Mint comes with more software than Ubuntu . You need 6 gig of ram to get full benefit of a 64 bit system