10.4.7 Home directory auto-creation (ANY creation!)

We're running into a bunch of automount trouble since last year. I'm not sure if it was an update (we ran four 10.4.5 servers last year, we run six 10.4.7 servers now) but this year, we can't get home directories to auto-create. We've followed all of the right steps and now get a strange new authentication error in /var/log/system.log, shown below: Oct 2 15:00:54 SJPS-OSX1 automount[213]: Can't mount sjps-osx1.sjschools.org:/Shared Items/home_directories on /private/Network/Servers/sjps-osx1.sjschools.org/Shared Items/home_directories: Authentication error (80) I haven't been able to find much info on this breaking in the middle of it working, we've been working for a year now. Kerberos works great, forward and reverse DNS are peachy-clean, automounts in OD look clean (the mount in the error SHOULD work, and does automount fine on the clients, clients work fine as well). thoughts/anyone? Thanks!