Firefox 1.5 and Javascript

Not sure if anyone else has noticed this or not, but there are a few websites out there that cause my cpu usage to max out. I first noticed it shortly after installing Firefox 1.5 and visiting any oreillynet.com website. It appears as thought it is caused by something in the sites javascript because disabling it returns my cpu usage back to normal. I have noticed it both on my Mac and my Linux box. Maybe it has to do with the firefox extensions I use, but I have not tested that yet. Hopefully someone else will notice and fix it soon. In the mean time, it is really starting to bug me. Especially when I am trying to conserve battery life.