Test results:  the modules are not the problem.  We blacklisted each one in the
diff list, but all tests gave identical results.  The USB disk was not detected
properly.

But good news, a different test isolated better.  Here is the full USB system
that grml 1.0 CD-ROM botches:

PC --> USB 2.0 Port A --> USB 2.0 Disk
     --> USB 2.0 Port B --> USB 2.0 Hub --> USB Scanner

Removing the USB cable to the hub makes grml 1.0 CD-ROM recognize the USB Disk
(with udev on, no special boot options).

So the bug happens only with the hub plugged in.  Then grml 1.0 fails to see the
USB Disk.  If the hub is unplugged, udev works, and grml sees the USB Disk.

grml 2.6.18 handles everything plugged in, very reliably.  So it is not a USB
hardware glitch.  In fact the hub is practically brand new.

Let us know what other data you want.  We're pretty convinved it's a udev
hotplugging issue - maybe the timeout is too short? - udev in 2.6.20.11 is
having problems with USB hubs.

We can try the 'grml nousb nousb2' test tomorrow if it will help.