That is funny. For in my case it is exactly the reverse. I can mount my USB Stick in 2.6 but not in 2.4 ! And it doesn't automount.

I have to make a dir
# mkdir /mnt/usb
#mount /dev/sda /mnt/usb

And even after this I have to open the USB hard disk as a root. But I am living with this as my Toshiba Sattelite HD controller has crashed and I jave no choice but to use Knoppix. The motherboard of Toshiba is not available where I live. i.e. Pune, India

By the way if you see the source code for these USB Hubs and drivers, you may realise the complexity and as the whole effort is by volunteers, they may not have sufficient testing facilities to test all releases for all types of hardware.
I guess that is why this forum comes in handy.