USB booting :: can't umount /dev/sda1 after booting from USB

If I boot from HD/CompactFlash (just the Bootscreen) and
then load DSL from USB (sda1) - i can't umount my USB-Stick.
Even if i use the toram option. "umount -> device is busy".
Is this a DSL-bug?

I think I use v1.1rc - how can I determine my exact DSL-version?

byebye & thanks in advance...

When you execute "mount" to list all mounted devices, what do you see?

original here.