Ask Max: How can I restore my scrolling ability?
For some unknown reason, something in the 10.4.6 update seems to have messed up my scrolling abilities system-wide. I've tried disabling all my customizations and hacks, but to no effect. What gives?
I have heard of many Mighty Mouse users losing the scroll ball features in 10.4.6 and I would not be surprised if the same problem would affect many other mice. As a first step, repair disk permissions and download and install the 10.4.6 Combo updater. Since you said that you customize and hack your system, I think there is a possibility that some files are not being updated properly in the standard 10.4.6 update. Installing 10.4.6 "Combo" update will replace many more files than a standard update and I would recommend always using the Combo updates if you change system files often. That may fix your problems, but it is likely that you may need to change the scroll speed settings. If there is a flaw with 10.4.6 and scrolling then changing the settings may act as a work around until a later update fixes the problem. If you have the opportunity, try different mice on the system, as it may be a problem with just one kind of mouse.
Let me know how it goes. I tried to keep this short so you didn't need to scroll down to read all of it.