I repeatedly experienced this problem with different audiobooks:
When drag'n'dropping a full folder of mp3 files (yes, the folder and NOT the single files from INSIDE the folder) into winamp the order of the files is not ok.
Instead of 1 2 3 4 5 6 7 8 9 10 11 12
it somes starts at another number till the end and then begins with 1
ie. 6 7 8 9 10 11 12 1 2 3 4 5
or 10 11 12 1 2 3 4 5 6 7 8 9
the mp3 tags seem to be ok.
But when copying the files onto another drive (with dopus) and then putting these newly copied files into winamp it works fine.