Have you found a solution to your problem so far. Because today I have exactly the same issue.
I have just upgraded my NSLU2 with the latest Debian release (lenny) and also bought some new HDD.
I even pay the fee to upgrade my twonky license to twonky 5.x but no armel build can work now and my NSLU2.
I have tried:
twonkymedia-armel-glibc-2.2.5.zip (my old version)
each time I'm ending with:
Starting ./twonkymedia ... ./twonkymedia.sh: line 97: ./twonkymedia: No such file or directory
Twonky team will you support us to have at least one running version for our favorite NAS ?