After upgrading from Kubuntu 12.04 to Kubuntu 12.10, I have a peculiar and very specific font problem. My default font all along has been Ubuntu 11. Now it shows up as bolded -- that is, Ubuntu Bold 11 and Ubuntu Regular 11 look exactly the same. I don't see this for any other size of the Ubuntu font--for Ubuntu 10 and Ubuntu 12, for instance, the regular font is thinner than the bold font, as it should be.
I've reinstalled the ttf-ubuntu-font-family package, but that hasn't made any difference.