ACLr8 is a command-line tool written in Python that will analyze your entire hard drive searching for files that cause the "ACL found but not expected" errors in disk utility, and remove all ACL from them.
Although these errors are relatively harmless, they can be quite annoying and they cause permission repairs to take much longer than they should. ACLr8 is very safe, but of course you use it at your own risk.
SNOWWHITESICKETTE Does just what it says. Also can be used to repair permissions. I had one "ACL found but not expected," and this got rid of it like a charm. (Leopard 10.5.8.) Thanks for this useful program! (Version 1.2.1)
THOMAS EVERS This worked. I read all the unix-flavored fixes to get rid of this problem in disk utility. That looked like a huge amount of tedious work. Ran this, and the hundreds of ACL errors are finally gone. Thanks! (Version 1.1)