A recent MS automatic security update (during the second week of April 06) looks like it might cause problems on machines with HP printer and scanner software installed.
The symptoms are Office apps freezing when you try to save or open files using explorer.
If you take a look in Task Manager and see a process called VERCLSID.EXE then you might be affected. If you have tried multiple times to open or save a file then you will have multiple instances of this process.
To resolve the issue, take a look at the KB article at