Adobe Creative Suite 5 and other Adobe CS5 software will require Firefox browser to be closed during installation.
Adobe’s Eric Wilde has posted this on the Adobe Installation and Licensing blog.
He lays the reasons and goes on to say: “This all applies to future Adobe Creative Suite retail releases. (sic: CS5, CS6, etc.) CS3 and CS4 installation will not receive the changes mentioned above and will still need browsers to quit.”
For more info on Adobe CS5 see Adobe Photoshop CS5 News Features Release Date Cost Updates.