How can I clean up when Synaptic screws up?

[soubeagi]

Preface #1: I posted in this section because it has "apt" in its title, but I apologize in advance if it should have gone elsewhere.

Preface #2: I use Knoppix for two purposes: A) to repair those other OSs when they get too badly screwed up to run properly, and B) to experiment with *nix technology in a way that won't crash my essential systems.

From Apt-get / dpkg tutorial:

that's how *I* learn. Not by man, not by asking questions, but by blowing it up and then examining all the little pieces, and finally publishing and asking for opinions. The nuclear physicist method, if you will.

For B), I do many things with Knoppix that KK and WPS specifically warn not to do, including (in my current case) trying to upgrade the preinstalled packages that come with Knoppix. I ask this question here because I haven't had any luck finding an answer elsewhere - not because it's particularly appropriate to Knoppix.

Preface #3: I'm not exactly a clueless newbie; when I started using Unix, it was an actual AT&T product on actual AT&T hardware, connected to actual terminals - but much of what computers do nowadays involves hiding the complexities of running them, making finding out what's going on "under the hood" (let alone digging around in there) next to impossible.

And now, on to the actual question: I recently tried to upgrade some of the packages on my Knoppix USB key, but one of the upgrades failed, and now every time I do anything with Synaptic, it keeps trying (and again failing) to redo the failed upgrade. (I'm deliberately not mentioning which package failed to upgrade, because I don't want to sidetrack this thread with package-specific discussions, or warnings about how bad it is to try to upgrade packages you know little about.)

How do I make Synaptic forget that this upgrade is pending, and stop trying to finish it?