Comment 2 for bug 675138

This is happening to me as well.
Today I tried to install starDict package from software center, it required the installation of some other packages which were not signed.
An alert informed me about that, but there was no option to proceed anyway, the only one was to cancel the installation.
I had to install it from terminal (sudo apt-get install stardict).
I would have expected an alert box with two options: "cancel" and "proceed anyway", not an error box with the "OK" button alone.