In Vista when you run CCleaner, it deletes the C:\Users\Username\AppData\Local\Temp\Low folder. This causes Internet Explorer 7 to give you an error message when attempting to print.
I have found a work around which must be done every time you are done running CCleaner. First you have to go to C:\Users\Username\AppData\Local\Temp\ and recreate the Low folder. Then you have to run the following command: icacls C:\Users\Username\AppData\Local\Temp\Low /setintegritylevel (OI)(CI)low
I responded to another post about this, but it wasn't in the bug reporting thread, so I thought I would add it.