On Wed, Jul 18, 2007 at 03:54:45PM +0200, Jan Danielsson wrote:
>    I want to use an USB memory key and a CF-card for storing certain
> critical configuration files on. However, using my memory key and
> CF-card under 3.0 was pretty unstable. As long as I didn't write large
> files, it worked. But if I pushed the interface, it could hang the
> system entirely.
> 
>    Under 3.1 the problem worsened, it is unable to use USB mass storage
> devices at all. (It does notice the attachment, but attempting to use
> the devices will hang the system).

Have you tried disabling ehci driver in your kernel?  On my machines,
ehci driver has always been quite unusable, but ohci works reasonably
well.

  -jm