I have the same problem and have been trying to find a fix for weeks!!

I am not sure if it it the fact the files are WMA as I have tried with MP3 and still had the same problem where all files are shown on the device in alphabetical order.

I have tried with Windows Media Player, Media Monkey and Songbird and the track order is always shown alphabetically. Frustrating as I also have all my music in WMA.

I have tried all various tagging options but all appear to be correct and I am stuck completely and really want to use my N900 for Music (with album tracks in the correct order)

Any help would be massively appreciated...

Simon