CUPS 1.5.3 has been released to public and for those who have been having problem with CUPS available on Slackware-Current (1.4.8), you might want to try out the newest CUPS version. According to the announcement, this version provides an improved USB backend based on libusb 1.0 and fixes a number of PostScript, SSL, authenticated printing, and networking issues.
I have updated my CUPS SlackBuild script to 1.5.3 on my SlackHacks and i also added a new SlackBuild for libusb. It's an updated version from the one available on Slackware-Current, and i hope this will bring improvements for USB-based devices, including printers and scanners. So that's why i added the latest version on my SlackHacks. If you want to test this CUPS SlackBuild, i would recommend you to upgrade/install/build libusb first.