重新安装Ubuntu 12.04后，无法安装商业游戏，例如Oil Rush。它给出了这个错误：
Failed to fetch https://private-ppa.launchpad.net/commercial-ppa-uploaders/oilrush/ubuntu/dists/oneiric/main/binary-amd64/Packages The requested URL returned error: 401
Failed to fetch https://private-ppa.launchpad.net/commercial-ppa-uploaders/oilrush/ubuntu/dists/oneiric/main/binary-i386/Packages The requested URL returned error: 401
Some index files failed to download. They have been ignored, or old ones used instead.
这些游戏我是11.10买的，但是我之前在12.04装过这些游戏。。。请问怎么解决这个问题？