Alrighty, that's a new one... it doesn't show you the USB logo in the top or anything when you connect? You shouldn't need any additional drivers or anything to get USB drives working, all the support is already in Chinook/Diablo. To troubleshoot, try checking to see if the tablet is correctly switching modes when you insert the adapter:
1) Open Xterm
2) type: cat /sys/devices/platform/musb_hdrc/mode
It should output "otg" or "b_idle" I belive... I'll have to doublecheck in later...
3) Plug in the USB adapter with your USB drive connected
4) do #2 again, it should now say
"a_host" I believe.

If it's not doing #4, then it's not recognizing the adapter or has manually been put into device mode instead of OTG mode...

Thanks,
-Rob