another problem you may be having is that even when your music is tagged correctly....or at least you think it is, if you have a tag input for say an album with a capital letter at the beginning then the same tag input for another song from the same album but that songs album name input doesnt have a capital letter to start it off then the music player seperates them. eg.

whitney houston - greatest hits
Whitney Houston Greatest Hits
both same songs same spelling but just because one has capitals and the other dont the songs in the albums get split all over depending what has capitals and what doesnt its so annoyimg. especially when you load 34gig of music onto the phone. hops in later firmware release they make it able to read folders an not just tags.
by the way as suggested use some software to batch tag i use TAG&RENAME. does a fantastic job an simple to use.