Can't mount movie DVDs after Security Update 2006-002

I installed Security Update 2006-002 today after all the preparation recommended by MacFixit. Everything came up fine, EXCEPT:
Movie DVDs (e.g., as rented from Blockbuster) no longer mount.
Yesterday, there was no problem.
Dual G5 2.5 GHz   Mac OS X (10.4.5)  


The following link describes MacFixit's recommendation for installation of 10.4.6, but it is basically the same recommendation as they have given for quite a while for any significant system update, including security updates:
Scroll down until you see "Update process recommendation".
In my case, I had followed the "more cautious route" of this procedure but still had a problem, and then the problem went away when I did a (presumably extra) pre-binding.
For system-wide updates (that is, 10.4.x -> 10.4.(x+1)) I've always used combo updaters rather than the supposedly specific-and-therefore-smaller updaters when updating the system. For the security update in question here, I downloaded the updater from the Apple site rather than use Software Update.
Hope this helps.
Dual G5 2.5 GHz   Mac OS X (10.4.5)