I encountered multiple problems when trying to update the firmware on my recently received Nokia 5610 XpressMusic. The original firmware version was 5.92.
I first tried the latest available versions of PC Suite and NSU on my Vista x64 machine. PC Suite worked fine but NSU never found the device. I then actually created a Windows XP SP3 install from scratch and had similar results: PC Suite worked fine but NSU never found the device. Out of desparation I tried my work Vista 32 laptop and to my amazement NSU actually found the phone.
I was ecstatic just to see NSU actually find the phone where I had no luck in Vista 64 and XP_32 SP3. Unforunately, the firmware update was now failing right after it rebooted the phone and the phone would remain in test mode indefinitely. I had to remove the battery to get it out of test mode. Well, after some amount of uninstalls/reinstalls/reboots, I was actually able to complete the firmware update to version 8.23.
In the end it worked out, but there are obviously some major issues with NSU.
Tony