The only solution to this I've found is to disable Windows Update from searching for updates by setting it to "Manual Updates Only".
However, this causes a problem in that every time you want to actually update, Windows Update may rebuild the entire "installed updates" database from scratch which can take hours on a heavily patched machine.
It's not related to the rebuilding or not rebuilding the "SoftwareDistribution" database (I've tried that) once the new updates exist, the traversal part is always slow, at least on Windows 7.
(The database is, fascinatingly, the whole 1 GB big).
However, this causes a problem in that every time you want to actually update, Windows Update may rebuild the entire "installed updates" database from scratch which can take hours on a heavily patched machine.