Hey Mare I just ran into the same problem myself
what I narrowed it down to on may machine was a conflict between Microsoft intellipoint 4.0 software for my mouse and the HP drivers
after uninstalling Intellipoint 4.0 my mouse would no longer work so make sure you have an older version handy to install afterwards
I used the intellipoint 3.0 drivers that originally came with my mouse
now my machine is happy again
hope this works for you
Kim
if it's not broken today it wll be tomorrow