Temporary Workaround:
Our two main concerns with parental controls is limiting access to websites we consider harmful to our kids and limiting the time our kids spend on the computer. We've found a workaround, that while not ideal, is getting us by until Apple gets this fixed.
First off, you have to disable Parental Controls.
Secondly, there is good news if you want to limit web access. We abandoned the Apple web controls a couple of years ago because we got tired of having to constantly "approve" websites that in our view should have been considered harmless. We've been using an app called K9 Protection. You won't find it inthe Mac App Store but you can Google it. It's free and it gets the job done. No hassles and no complaints. It's also available for iPod/iPhone/iPad if you want to disable Safari using parental controls on one of those iDevices.
Next, we found a timer that will "switch user" after it counts down. There have got to be better options out there but it's on the Mac App Store and I didn't have a lot of time to search around for something better. It's called Kidz Timer and it's 5.99. A bit of a rip off IMO for what it does. To get it to work, I had to change my kid's password so he couldn't log back on and give himself more time. What's also frustrating about the app is there is no visible countdown timer. It will just switch the user to the login window without warning when the time is done. You need to use a separate countdown timer if you want to keep track. Furthermore, there is no way to "pause" the timer. So for example, if your kid is allowed 1 hour and uses 15 minutes then logs off, you have to log back in and set the timer for 45 minutes and start the timer again. This is not an ideal solution for time limits and I'm sure there are other (and free) apps that would do a better job but this has been our workaround for the time being.
The good news is, you may find you like K9 Protection better anyway. I know we do. Good luck everyone. I hope Apple gets this resolved soon.