Using the hal packages from 13.37 has worked for me in the past - you will need to start the hal service (/etc/rc.d/rc.hald) then restart flash - this is because the hal version of the flash renderer is required for the DRM to work.
PACKAGE NAME: hal-0.5.14-i486-3.txz
PACKAGE LOCATION: ./slackware/l
PACKAGE SIZE (compressed): 464 K
PACKAGE SIZE (uncompressed): 2430 K
PACKAGE DESCRIPTION:
hal: hal (The HAL Hardware Abstraction Layer)
hal:
hal: HAL is a piece of software that provides a view of the various
hal: hardware attached to a system. HAL keeps detailed metadata for each
hal: piece of hardware and provides hooks so that system and desktop
hal: software can react to changes in the hardware configuration (such as
hal: the insertion of a DVD, or a USB flash memory stick).
hal:
hal: For more info, see:
http://hal.freedesktop.org/
hal:
PACKAGE NAME: hal-info-20091130-noarch-1.txz
PACKAGE LOCATION: ./slackware/l
PACKAGE SIZE (compressed): 48 K
PACKAGE SIZE (uncompressed): 400 K
PACKAGE DESCRIPTION:
hal-info: hal-info (device information for HAL)
hal-info:
hal-info: The hal-info package contains device information for HAL, a Hardware
hal-info: Abstraction Layer.
hal-info:
hal-info: For more info, see:
http://www.freedesktop.org/Software/hal
hal-info: