AFAIK, slackware's default udev.conf doesn't create lirc nodes. Here's a tip you might know, in LIRC source you'll find the udev info. You can include that snippet into udev.conf so your nodes are created. Apart from that, add MODE="0666" as well so it will have somewhat liberal perms.
I plan to do some testing myself this weekend to get this thing working. Earlier, I had custom compiled 2.6.22.6 kernel to use with my mythtv but lirc didn't work so I switched back to slackware 12.0 stock kernel and upgraded to 2.6.21.7 (using stock kernel's config). LIRC still won't work with 2.6.21.7. And all along I'm using lirc cvs. I'm thinking of going back to 2.6.20.x and see if I can get it to work.
I have slackbuilds for mythtv, lirc, ivtv and host of other stuff. Let me know if you need them.
Cross your fingers and hope this sucker works