sony netMD in kubuntu

It's not looking promising. Sony aren't good at releasing specifications for their audio devices so making software interoperate with them on Linux is somewhat problematic.

http://bugs.kde.org/show_bug.cgi?id=127586

I agree with Alan. I'm myself a sony NW-HW5 user and since I don't own a windows copy it's a long time since I'm after a solution with no luck at all (and I searched a lot). However I recently found something pretty useful:
I'm sure MDs and NWs are not quite the same (although both plays ATRAC and, to some, extent, MD plays them too) but _if your MD allow you to play mp3 and you want to import/export only mp3_ you could check NW-E00x Mp3 File Manager to see if it helps you: http://nwe00xmp3man.sourceforge.net/
Here you can read a step by step tutorial: http://www.lynchconsulting.com.au/blog/index.cfm/2006/9/26/Sony-NWE005F-working-in-Linux--HOWTO

mariano - unfortunately i own a netMD not HiMD and my player doesn't support mp3 (Sony MZ-N10), so as for now the problem is still "not solved"

In that case, so far, this is the most realistic option I found:
This tutorial explains how to make sonicstage work under vmware (you need windows for that but you'll be starting it from ubuntu): http://undocumentedcode.com/?p=15

Or if you don't like VMWare, there's VituralBox and QEMU as other (more free) options.

https://help.ubuntu.com/community/VirtualBox
https://help.ubuntu.com/community/WindowsXPUnderQemuHowTo