Scanning slides on HP C8180 AiO

I scanned slides for the first time last night on my HP C8180 All in
One.
I used the Kodachrome setting, 2400 dpi, with 4 slides.

PC is an HP laptop, Windows XP Professional, version 5.1 SP2.

It kept scanning for over 3 1/2 hours before I hit Cancel! (I know it
should be slow, but not that slow?!)

I think it was scanning all 4, then automatically starting over again.
(I think this because at some point I noticed the normal "at rest"
menu came up on the AiO. Then it started scanning again.)

Any ideas as to how to avoid this problem?
Thanks!