[Bruck]

how do I reverse?

[Dr. Wahnsinn]

You can try installing the update again. When I installed the update, my Mac froze and I had to force restart. iCal didn't work after the reboot but running the update installer again solved the problem.

[mishakim]

are you sure you're trying to run the new version? In my case, since I had moved it, but Apple's installer still insists on putting things directly in /Applications, it didn't overwrite the old one. Clicking the old one (still in the dock) bounced then quit without any message. Once I saw that the new one was in a different place, I moved it to where I wanted it and removed the old one. Also had to remove & replace the dock icon.