I too am having this exact problem but cannot fix it. Model is MZ-N910 and Widows 7 64 bit. I have installed the latest driver from this site and the player shows up in 'devices' and says it is working ok. The driver details are "system32DriversNETMD760" Is it correct it states 32 and not 64? It does not show as a mass storage device under my PC, should it?
I have installed Sonic Pro Ultimate from this site but it won't run. I have tried various compatbility settings and it opens for a few seconds then says 'programme stopped running'.
I would really appreciate any help to get Sonic Pro running so I can use the player with my PC. Thank you.