Chrome not working with activity monitoring/blocking on Mac OS X (Snow Leopard)

Hi,

 

I can't get blocking to work in Chrome (my kids preferred browser, the first thing they do when the log into a computer is look for Chrome and if it isn't there, install it). It works in Safari (FF isn't even installed) but not in Chrome. 

 

I  thought the application worked at a deeper OS level, and Chrome uses the OS level infrastructure (including proxies), so how come it doesn't work?

 

My kids have been told they can't have their laptops back until I get monitoring working, so they would like a workaround as quickly as I do.