Under /Library/Receipts, there are a bunch of files ending in .pkg. These are what Software Update uses to determine what updates you need.
Try removing MacOSXUpdate10.1.1.pkg and SecurityUpdate10-19-01.pkg and reinstalling.
As a matter of fact, try to remove the OSX update pkg first and see if a re-install does the trick. If not, you may want to delete the Security Update receipt and re-install that.
Failing this, wiping and reinstalling your OSX partition will probably work as well.
(You do have your data backed up, right?)