I have both a Nokia DKU-5 cable & a PL2303 clone DKU-5 cable.
Nokia PC Suite 5.05, installed on my wife's laptop, works but
only with the Nokia DKU-5 cable. Unfortunately, Nokia's deal
with Verizon ensures that PC Suite is useless for my needs - see
my
Verizon rant
for more "information".
I am now using Slackware 10 updated with kernel 2.4.28
I downloaded gnokii-0.6.4 & have yet to give it a try.