HP ScanJet 4Si double-sided

hi guys,

i've got a HP ScanJet 4Si that's a network scanner with ADF and DUPLEX
(double-sided) feature. The problem is, if i scan a double-sided
book, the pages don't show in the right order. If i open the scanned
book in PaperPort, the 40 front pages come first, and then the 40
backside pages. Instead of, frontpage, backpage; frontpage,backpage..
and so on...
I use Win98 and use Netware
firmware version is 1.03A, the latest one.
also admin and client software are up-to-date...

Any suggestions, ideas...?
thx!