I have Ubuntu 8.10 64-bit installed and everything works perfectly. It is not
likely a 64-bit vs 32-bit issue. Have you checked out Launchpad to see if this
is a bug peculiar to your hardware? The greyed windows sounds like a graphics
card issue. Are you running Compiz, BTW? Try installing Compiz Fusion Icon from
the repos and toggle Compiz off to see if it still is a problem? Try installing
a different desktop such as KDE because different window managers can make a
difference.

Firefox should not be an issue unless you are running the experimental release.
Try removing it and all of its settings and re-install and try to download
without any add-ons installed. It could be an issue with an add-on. If not
contact the Mozilla folks directly.

USB works fine for me. Which version of usb do you have? Is it usb 3.0?

It may be something that will be improved with the next kernel as you system is
quite recent. There is always a lag because of the way Ubuntu does it. Drivers
are not included separately and OEMs don't always cooperate with kernel
developers, so there is often a lag between releases.