MySQL 5.0.27-max xserve g5 dual run very slow

Hi to all,

I have a very strange problem on my dual G5 xserve running php and mysql5.
I upgrated from mysql 4.01 to mysql 5 5.0.27 and now my server is very slow during queries.
My CPU is always used at 45% by MySQL and I have not too much connections or users at the same time.
I found this link: http://www.shawnhogan.com/2005/10/mysql-problems-on-mac-os-x-server.html that explain something about mysql 5 on xserve.
Is very strange if I reboot mysql it runs normally but after some queries it returns slow again...

Anyone has some idea?

Thank you all
Yorh