Hello, I don't use Slackware, but I've seen your thread in the zero replied ones at that time.
I can try to give you some ideas :
1) Unplug all removable devices which are not automounted anymore
2) Restart the hald daemon
lshal > listhal0
4) Plug in one removable device
lshal > listhal1
6) Look if the device was recognized by hal :
vimdiff listhal1 listhal0
If it is, then you know that hal is working correctly, and the problem comes in an upper layer of code, maybe at WM/DE level.
Try to logout/login and continue to investigate from there.
There is the KDE log file for a user in $HOME/.xsession-errors file.
Sorry if I will not follow this thread, because as I use another distro, I don't go into the Slackware forum.
Maybe someone who does will answer you after you tried what I suggest here.
Good luck. Bye.