Can I fix things so Archive Utility doesn't hang on all zip files?
It's related to the Apple Events bug in 10.8.2 that also makes revealing files in Finder stop working.
As a workaround, you can terminate the appleeventsd process with
sudo killall appleeventsd
sudo killall -KILL appleeventsd. (Without -KILL the process is sent a TERM signal and many processes stop responding as @myhd described.)
I have run into this a couple times, both in instances where I didn't have time to dig into the cause. A restart will recover from the underlying failure between finder and apple events server so that you can unzip files, but that's not ideal since the underlying condition is likely to be triggered again.
As it has become clear that an OS bug is causing the hang, I keep a copy of the free app The Unarchiver in my Application folder.